You might want to remove the name of the retailer, non-AV members can view this forum.
If you are looking for a gas powered rifle, you should figure out what model/type you are looking for. Do you want something that is armalite (M4/M16) based? Or maybe something more ambidextrous like the SCAR? Or a long rifle like the M14 or a bullpup like the L85? Or an AK style rifle?
All of them will perform pretty much the same out of the box. You can further install upgraded parts to improve performance. Almost all of their gas rifles fall within your price range.
If by 'gas powered gun' you meant a gas pistol, then I'd recommend something from Tokyo Marui or KSC/KWA. Don't think those are stocked by that particular retailer.
H&K G36c (KWA) / Glock 18c (TM) / Kimber LAPD SWAT Custom (TM) / Mossberg M500 (ACM)