#1
Well i mainly play classic rock and am looking for an amp in the 300-450 price range and ive been looking at two main amps... the b-52 112 60w or the peavey valve king 112
Which is better for classic rock and the pros and cons about them?
#2
neither i'd say. you want something that's more of a crunch sounding amp. blackheart handsome devil, peavey classic 30, traynor (used) yc40 or whatever it's called. peavey windsor 20 watt combo.

i say get something with EL34s if you can, i prefer those over EL84s b/c they've got more balls, but it's definitely still a preference thing when it comes down to it.

hope that helps.
My MAIN Gear
____________
"They call him the 'Sand Spider.' -Why? -Probably because it sounds scary"
*Agile AL3000 Les Paul w/ Alnico IIs
*Randall RM50
*Dunlop CFH
*fellow LEO feel free to give a shout out
#3
I don't know about those two, but there are many other choices.
As slash_rocks said, the Blackheart Handsome Devil and the Peavey Classic 30 would be good choices.
You could also look into used amps, like an Orange Tiny Terror or a Traynor YCV50, although they're a little over your budget.
If the most sought after things are often the most simple, then:

6 shoelaces of varying sizes tied onto a branch
+ 1 Quarter (pick)
----------------------------
= ULTIMATE TONE
#4
well the b52 can do classic rock but its more suited for high gain stuff.