I think that yes. 400 dollars are nothing for an amp and a cab. He mentions in the ad that he will negotiate the price down. So you can probably get it for 350$.
I'm using a 400rb amp which is enough for me. I had the chance to use both 700rb and 800. The 700 sounded close to the 400rb which I liked. The 800 had way too many options in it which drove me crazy. I didn't really like the sound I got out of it, but that might have been the cabinets in use(two gallien kruegers - 1X15 and a 4x10 I think).