I know a guy who is selling a V4BH and an SVT410HLF for $900. Assuming everything is in good condition and fully functional, is that a good price? I'm still a newbie on a lot of this stuff, but from what I've been able to find on the internet, it seems pretty fair. I thought I'd get another opinion, though! Also, I don't really have any experience with tubes. Is there anything I should check out when I look at the setup? What about eventual tube replacement for the V4BH? How often are tubes replaced, and what does that usually cost? Thank you all!