Preamp and DAC combination for upgrade

issue: wondering if I can get a single unit preamp/dac as part of upgrading 2 channel listening. And, if so, what are some good options.

I currently have the following system:
NAD T765 A/V receiver
Quad 12L2s (Front L/R) with Quad Center and mini monitors for surround (MIT cables)
Sony blue ray and HD cable box and sonos

I would like to improve two channel listening by purchasing new amps (looking at Bel Canto, Wyred or NuForce mono blocks) and dedicated, higher quality CD player.

Goal would be to have:
1) the 2 channel system for listening (cd and sonos source through "pre/DAC" to mono blocks driving 12L2's and REL;
2) 5.1 channel for movies and TV (NAD 765 serving as processor for dvd, cable and driving center and rear speakers with a line level pre out to new pre/pro so 12L2's and REL in "2 channel set-up" will be the Front L/R and sub when needed for 5.1 system.

My question is if there a preamp/dac combination that would work (instead of buying separate preamp (for pass through from NAD for 5.1) and DAC to get quality sound out of the digital sources).

Thanks for any help/insights
The Benchmark DAC1 Pre and the remote version come to mind.
Check out Music Hall, Raven or Mambo. Both have built in DAC, should have pre-outs. The Raven has tuner, Mambo is integrated with Class A amp.
Thanks. the Benchmark looks really interesting and the analogue RCA input should be fine as a pass through from the pre out of the NAD. I will also look at the other ones mentioned.

Thanks bob and Elevick
Great suggestion from Bob. You may want to consider your speakers before investing heavily in DAC/PRE and powerful monoblocks. The Quad 12L2 are great but they are kind of one step above entry level - remember your speakers make the biggest impact. Two cents...
Don't disagree on the thought of speaker upgrade. Here is the rationale:
- 12L2s sounds great out of the NAD and I was recently able to hear them driven by Bel canto 500 - sounded incredible (REL sub helps really bring out bass on orchestral music).
- I can do the benchmark, bel canto CD2 and nuforce/wyred/bel canto amp at around $6-$7k all in (a'gon purchases);
- The speaker upgrade is next - have listened to Dynaudio Confidence C2 with good class D and really incredible - $12k - next year.

FWIW - class D seems to have gotten good enough that the green side of me would not consider large wattage, large footprint class a/b.
Just a thought here, put the PS Audio Trio A-100 amp in the mix with your other Class D options. They are so reasonably priced I am using two of them in bi-amp configuration. I am using a Bel Canto Pre3 into the A-100 balanced inputs. In a small room they sound very nice into my Quad 21L2s.
I just got my system set up - ended up with a wyred4sound ST-500, PS Audio pre-amp (GCP-200; recently discontinued by PS Audio and was able to get cheap and new from PS Audio directly) and PS Audio DAC III with Cullen stage three upgrade (through a'gon). was also able to fine a good deal on the Quad 22L2 speakers - very incredible floor stander for the price. The sound is reallly remarkable.

thanks for thoughts/suggestions