Importance of Amplifier versus Preamp?

Definitely play around with the various ways identified to hook the gear up. Listen and compare. Only once you have it set up the way that sounds best should you consider any next steps, if still needed.

If you decide to go the tube integrated route, here is a very modest cost way to give it a try:
http://app.audiogon.com/listings/tube-audio-space-as-3i-integrated-el-34-tube-amplifier-in-factory-box-2015-01-28-integrateds-80020-broomfield-co.
No relationship to seller, never heard the amp, etc., etc.

Therefore, after all those advices, the quandary becomes: I will keep the Sony and the SAE ,but I need to upgrade the speakers.
What would be good floor standing used speakers for $1000?
Should I go vintage, or current? Hum.........

Apologies if this is just too far off your initial inquiry, but maybe the amp/pre are fine. For $1500 you could have a really good front end--Used Windows laptop ($300-$400,) jRiver software (on sale today for $44.98,) Wireworld Starlight USB cable ($100,) and a used Benchmark DAC1 ($500), and you still have $500 for great source material.

This would position you towards the future of hi-res, and also Internet Radio and perhaps Tidal.

Buck for buck, for me this was the greatest improvement in sound quality, access to music options, and even reduces the cost of feeding it.

SAE's used to be the dealer's amp of preference for OHM speakers.

You can buy vintage OHMs used for not much, buy upgrades for any model still from OHM, or buy new refurbs or totally new speakers from OHM as well.

Just one option. Many others as well. Read up on what's out there first before deciding.