My friend is looking to by a new bass amp 50 to 200 he wants. He plays alot of metal like slipknot and enslaved and all that kinda stuff. He said he range is around 500 for a half stack or combo. And I don't know alot about bass stuff so I need your help.

This is the one he is looking at.
kustom kba 115c 1x15 200watts
Gibson Thunderhorse
Jackson RR24M
B52 AT100
bass amps in the 50 to 200 watt range and basically good for small band practices and not much else, what's he looking to use it in (a band environment, home practice?)
Peavey 6505+
Fender Hot Rod Deville 410
Fender Telecaster Blacktop
Gretsch G5120
Tell him to take a look at this amp.
Peavey TNT 115
I have the previous version of this amp and it sounds great and has never failed me. This thing gets loud.
Fender 5 String Jazz Bass
Fender Precision Bass
Peavey TNT 115
EHX Bass Big Muff Pi
Daneletro Cool Cat OD V2 (excellent pedal)
Paul Reed Smith SE Custom Semi-Hollow
Peavey Classic 30
Vox V845 Classic Wah Pedal
If you want to wait two months for the TNT, I think it'll be excellent.

The Kustom is also a very good amp, and seems much louder than 200W. I've done jazz gigs with my 16 w 110 :P
$500 is not a stellar price range to be in, but maybe look into upgradable rigs (i.e. half stacks) that provide quite a bit of wattage. Look into Ashdown and Hartke, two very different amps, but in similar price ranges with similar wattages. Also look into Carvin, if he's willing to spend a little bit more; you probably won't find anything great for $500, but for a little bit more (in the $700 range) you could find something worth several times more than an Ashdown or Hartke. Also look into Acoustic. Not great amps, but fairly cheap and similar to Ashdown. The other thing I recommend is get a 115 not a 210 to start you stack off with, especially with the type of music it's needed for.