Arcam AVR350 vs AVP700+amp

I currently have a Yamaha RX-V1300 receiver, and I'm about to take the plunge into a more high-end setup. Funds are a bit tight right now, so I'm looking exclusively at used gear.

I originally was looking for an Arcam AVR350 to replace the Yamaha, but I was wondering if a good alternative would be to pick up an AVP700 (and keeping the Yamaha as an amp), and then upgrade the amp later as funds permit.

I'm sure this wouldn't sound as good as having a dedicated, high-end amp, but do you think this would be a foolish idea? Would the Yamaha amp section negate the upgrade to the Arcam preamp section?

Yamaha RX-V1300
Oppo BDP-83
Paradigm Titan v3
(plus center + sub)

Eventually I want upgrade everything (my thoughts right now are to replace the Titans with Studio 60s or 100s, the Yamaha with an Arcam pre, and a dedicated amp) but I'm going to have to do things one at a time... figuring out the best order to do it in, to get the most noticeable and positive improvement at each stage, is driving me nuts...!
Definitely something I'm considering as well (with an Emotiva XPA-5 high on my list).

I suppose this raises a related question: which has the most impact on overall sound quality (particularly for music), the amp or the pre?
Use the Yamaha as a pre and buy a really nice amp!
It will probably be the best sounding of your choices and the least complicated compared to having to pre sections involved.