I am wondering what way to eliminate the feedback. Yes, I know about room acoustic, but it's difficult to change that.

I can think of three ways:
1) Noise gate/noise supressor. work with noise, but does it work with feedback?
2) EQ. Eliminate a certain EQ... also changed the tone
3) Feedback eliminator. Expensive and comes in rack form only (I want stompbox)
Ibanez SA-120 (ed.2006)
BluesJr 1996-B + cathode follower + texas Heat
Crate CPB150
Homemade 4 x 10 cab Bass closeback
Metal Muff
no...if you get an isp eliminatior...thats a stompbox...check it out..i have the rack version and its sick...
Wow umm... check out the billion and a half products they say Noise gate, Feedback elimiator so and and so fourth blah blah.

Now here are some cheap ways.

1) Don't play in a room with Computers, Tv's, Stereo's. They can cause feedback, or sometimes they turn your amp into a really bad radio.
2)Don't use so much GAIN!. And back off on the Presence if your amp has one.
3) Get a good surge protector, most of the good one's will get rid of hum and that sort of thing. And will keep your stuff from getting fried in an thunderstorm.

If all else fails just get a noise gate.
The Boss NS2 is perfect! [And it only costs $100 (USD)]
My Gear:
Peavey 6505+
Marshall 1960B
Schecter Hellraiser Avenger
Ibanez VBT700
Marshall Guv'nor
Marshall Echohead
Morley Tremonti Wah
Boss TU-2
Boss NS-2
Avatar 2x12
EHX Holy Grail Reverb
Furman SPB 8C
Boss Flange
Not sure the problem Im running a tube amp and can crank the gain on the lead channel to max with no feed back unless I want it. I can stand 5 feet from the amp facing it with no problems. I dont use a noise gate or anything like it. Biggest thing to increase feedback is running really hot pickups with the guitar volume dimed. And running to many distortion/OD pedals in series before the amp. I use a TS9 turbo but keep the gain on the amp down so I can boost it really easy then back it off real easy to. I keep my guitar volume at about 8 so I can always add if I want.