Is a peavey firebass and a matching 700w 4x10 a good deal at $350
Assuming the rig is in good condition and it gives you the sound you want, then yes; that is a decent price. The Peavey Firebass was somewhat popular for a while. As I recall, it was made in the U.S.A. I have little direct experience with it, but people do seem to like them and it is a powerful amplifier. I believe the white face version was slightly more popular than the black face version, though they may be the same amplifier save for the cosmetic differences.
it's a red face/blackface whatever think I could go lower?
$350 for a 700watt bass 1/2 stack, buy it if it is in good condition.
Assuming the rig is in good condition and it gives you the sound you want, then yes; that is a decent price.
+1. Older Peavey amps like the Firebass, Megabass, and Mark series don't exactly have a lot of resale value these days. If you're getting both the head and a cab, and both are in good working condition I'd say you're getting a decent deal.
Remember though that it only puts out 700w at 2 ohms. Its rated at 475 at 4 ohms, and 275 at 8 ohms.