jglim,
Maybe we could steer you in a better direction if we had a budget to work with too. If you are just building the System around the ST's(great start BTW) I would rank the following in order of priorities to start with:
1. Speakers (choosen already) make the biggest difference second to room placement & treatments
2.Preamp - handles your analog sources, even mid level priced ones will outperform most AV receivers(in 2ch)
3.amp - dont need to spend huge $ here, something used on audiogon that has sufficient power(shoot for around 150WPC) maybe in the $500-$1000 range for 2 ch.
4. Source such as a Squeezebox or SONOS setup - same quality as CD player but offers more storage & ease of use.
5. A Seperate DAC - to me this should be the very last item you consider being it makes the smallest difference in a setup, again my opinion. I won't dive into this camp publicly here

As for what which brands & etc for the items above, well thats the tough part

Take a look around at the used market and what others find works for them and run some ideas past this group, you will get some excellent advice.
Brandon