Got an Adcom 5300 to power my Vandies and MA Silver 6's... Now What?

So I finally bought a cheap dedicated amp for my Vandersteen 2Cis and Monitor Audio Silver 6's...  Now What???

I have some solid power now, but now I am working on ways to play my hi-res files off of my computer and occasionally play some CDs.

I have been looking at combo DAC/Preamps such as the DACMagic Plus from Cambridge, the Teac UD-301 and Marantz's HD-DAC1.  But, is this the right way to go??

Most of the preamps under the $1,000.00 price range don't appear to be competitive options compared to the DAC/Preamp combos.  I thought about buying an Adcom GTP-450 to match the 5300, but I am not convinced that it will outperform any of the combos either.  I even looked at the XiangSheng 728A (Which looks like a real gamble with it's made in China stamp and lack of any respectable dealers and/or reviews).  The NAD 165BEE looks like a good option, but they are expensive and I would still need a DAC.

I find myself wondering if using my old Onkyo receiver or even my Sony E2000ESD as a preamp might be my best option until I have the funds for something better.
For price and performance, I would look at Schiit. You don't need to spend a lot to get something killer.
A Sys and Modi would probably be the way to go with your Adcom, and would cost under $200. They even have a 15 day return.

the Adcom is a mosfet power amp and will mate nicely w/ your Sony ES pre-amp until you decide on more purchases. You may even grow to like the sound of these (2) components.  You will not need fancy cabling, either.

Happy Listening!
As jafant stated, use the Sony as pre for now. Take your time to best identify your needs and the marketplace.

If in need of a DAC for computer audio, one option I use in a 2nd system is a HRT Music Streamer USB DAC (which can be found for ~$80) with a pair of male to male RCA  plugs (no cable) connected directly into line level input of pre.  
Thank you all for the answers.  I will stick the Sony E2000ESD for now and start researching the options you recommended.
The Schiit products look interesting, especially the SYS, which is a passive preamp.  I read in another post that there are a lot of benefits to skipping the preamp stage and just using a potentiometer like the SYS between your DAC and Amp.  

I own a Schiit SYS. Worth trying one out at ~$50. Use short interconnects (0.5 M).