Sound quality impact - preamp vs power amp?

The week link in any system will ruin the entire thing.

Yes but be patient, it can only take so much and so at 2 weeks the link breaks.

Take a $50,000.00 system and feed it low quality source and it will sound like a big awful system.

Actually it will sound like a big awful recording. A friend who is really into the Rolling Stones loaned me a whole bunch of their CDs. Until then I always thought Springsteen was the king of great music crap recording but no, its Mick. 

A truly awesome system has the ability to recreate a whole new world. Its not the system's job to sound awesome. Its the system's job to sound like whatever world is on the recording. Whether it be a magnificent concert hall, a magnificent recording studio, or a magnificent 1968 Ford pickup. Don't know why anyone would want that, but there it was. In all its glory. 6x9 coax. Green vinyl dash. With a crack in it. 

The acceptable phrase is silk purse out of a sows ear. Either way its bollocks. A better preamp will be a better preamp and an improvement regardless. Speaker amp problems are speaker problems. Trying to solve the problem of a hard to drive speaker with an amp is a fool's errand. 

People asking about separates while pretending to care about cost always make me smile. If you really do care about the cost/performance ratio, in other words value, the answer is almost always an integrated. With integrateds like the Raven Reflection you have to go pretty far up the high end food chain to be looking at separates- and then you're talking $50k not the (relatively) measly $11k the integrated costs.

But the audio community has guys so spellbound buying ever more stuff, and separates do help you buy a lot more stuff. You can get mono-blocks, bi-amp, and lots and lots of power cords and interconnects.