I know Quad had a good reputation. I’ve an opportunity to acquire a Quad 303 power amp and a Quad 33 pre amp.
Are they worth a punt and how much are they worth ?
Unless they are 
I wouldn’t bother.
Pre amp is 
Some people love 'em, some don’t. In James Moir’s Quad II vs Quad 303 vs Quad 405 listening test people who thought they could tell them apart couldn’t once they weren’t told the answer in advance (not for the first time or the last).
The best guide to value is eBay completed listings, bearing in mind the condition and any mods. The 33/303 combo shouldn’t be expensive so the risk of loss should be low if it turns out that they don’t suit you.
One thing that would be worth checking is whether the pre-amp input sensitivities match your sources.
VB