When we practice (normally 2 guitars and 1 bass) but when we start jamming i dont like the sound, i know is the amps cuz we all can play it alone and it sounds good.
i dont have any idea for the settings of the amps.. lets see.. for practicing
we have one Guitar Amp Ibañez (20w) with: Volume,Bass,Trebble,Gain,Middle.
we have another Guitar Amp Marshall (20w) with: Volume,Gain,Trebble.
And a Yamaha Bass Amp (12w) With: Volume,Bass,Trebble,Gain.
we dont know how to... set up for playing in group, example: i know that the guitars have to sound a little more than the Bass.. i hope you understand what i mean. what a try was putting the 2 guitars with: volume-7 Gain-8 Trebble-5
and the bass i dont have any ideas how to set it..
i will put the covers we are trying to play if u need it.
Symphony Of Destruction - Megadeth
Iron Man - Black Sabbath
Paranoid - Black Sabbath
The Trooper - Maiden
Hallowed Be Thy Name - Maiden
Aces High - Maiden
Enter Sandman - 'Tallica
Hearts On Fire - Hammerfall

thx in advance.. also if you have a must-know document for amp settings ill be very thankfull
Well, I'm no expert on amp settings or anything, but our band usually (which seems to play similar music to you) has both guitars with boosted bass/treble with the mids pretty scooped. My bass has the treble cut to about 10 o'clock, the mids boosted pretty high at about 3 o'clock to fill in the gap left by the guitars' mid-scoop, and the bass a couple notches below the mids at about 1 o'clock.
Well, judging by the wattage on those amps I'm gonna go out on a limb and say you just have bad amps.
First step is, don't scoop your mids. A lot the the power from the guitar is in the mids. It's okay to maybe cut them a bit if you want, but don't scoop 'em right out. And maybe try cutting some of the bass off the guitars, that what you bassist is there for!

Now, the second and far more important step is to GET NEW AMPS!

If you go solid state for the guitars you should get around 30-50W. If you go tube you'll need less, I play my 5W Valve Junior combo with my drummer and have no trouble being heard. 10-20 watts would be perfect.

Bass needs a lot of clean headroom, so triple that for the bass amp. Anywhere from 150-300W SS should do you fine.

I'd advise you don't get half stacks. They look cool, but are a pain in the ass to move around and are totally unnecessary. Get a couple of nice combos. This goes for the bass too. You can always add extension cabs later if you need to push more air, and most places will have a PA to mic up to if you need more volume.
if what was already suggested dosent work, try to make the bass as clean as possible, or slight fuzz, just dont have it really bright or distorted or anything. Have one guitar scooped,distorted, and on a really low, bass like "chugg" (rythem). Have the other guitar brighter and "pingy"er(lead). if the sound is too similar they will cut each other out. And when I say Rythem and Lead guitar, it doesnt mean that both guitarist dont solo or take lead, just that during the normal riffs have (especially if your changing a song to include two guitars, i dont know if that is what you are doing, but just to say... try doing the riff in the normal place with the lower end, or a lower place and have the higher pitch at a higher octave.) know that one will ring out more, but personally i like the "rythem' guitar 'cause its the "brick wall" of the total band sound. AND THIS IS ONLY A SUGGESTION! try out all the ideas and deside as a band which is best!

Gibson SG
Epiphone LP
"Apocalypses Guitar"
70's Silverface Bassman Amp
Russian Bigmuff
Digitech Deathmetal Pedal
Digitech Badmonkey Pedal
Boss Tuner
this is our amps for practicing, in stage we have a 100-150w but in stage we have a team that equalize all the amps and that thing, so we dont really know about this, only play.
I'm guessing they are Marshall MGs and Ibanez Tone Blasters. this is funny cuz me and the other guitar player in my band are using these. The MG is better than the TB, but not much. If u are gigging soon i'd say get Tube amps, if not, just use what u are, it's better to just wait and get a gigging amp than to buy 45 amps between then and now. We aren't in a big hurry to buy new amps as we have probably 4 years until we will be gigging.
ESP F-200 with Floyd Rose>

Ibanez Weeping Demon Wah
Electro Harmonix Pulsar Tremolo
BBE Boosta Grande
Fender Pedal Tuner>

Peavey Valveking 1x12
I know this is a useless reply, but...
That song list rocks! My band does those exact same songs, except for Symphony. Hearts on Fire rocks! We have about 4 originals, too, though...
"There is no hell. There is only France." - Frank Zappa
I really doubt the problem with the sound is in the amps especially as you said that you all sound fine independently.

Yes they are not great amps but you can still get a good sound out of decent amps.

The real problem is probably one of two things or both. Either you are not in tune with each other or you are not playing in time together. If you fix these things you will sound a lot better.
WARNING:This post contains explicit portrayals of violence; sex; violent sex; sexual violence; clowns and violent scenes of violent excess, which are definitely not suitable for all audiences.