I'm thinking about purchasing a 6 year old Mesa 2x12 Recto Cab from someone for $425 CAD (about $408 USD) to replace my 1960A since I'm annoyed of gigging with a huge 4x12. It's loaded with V30s that are broken in, and has just a bit of wear and tear. It'll be running with my Peavey 6505.

Should I go for it?

It's a decent deal, nothing too fantastic. Excellent cab, and worth the money. However, like Denied said, you could probably drop it by $50-100 more if you're persistent.
Standard Strat
Jackson WRMG
Parker DF724

Axe-Fx Standard
Carvin DCM1000L

Mesa Trad. Slant Recto 4x12 (UK V30s)
Custom Horiz. 2x12 (Commonwealth 12s)