First thing I would ask is what currently is wrong with your current setup? Have you run any tests on your current DAC to see if it has any problems or room for improvement other than cost? To me if you are looking for a different sound change your headphones. If you do not have any already try a pair of AH-D2000's or LCD-2's. I really enjoy their sonic signatures especially out of a really flat output amp.
As we say in the biz: "If it ain't broke, why fix it?"
If you are tired of your setup and want something fresh I would trade your setup for something comparable in a completely different headphone regime.
It sounds to me you expect to be able to upgrade but really have no idea if an upgrade would actually improve your listening experience.
That said I would like to end in a quote from Headroom:
"...the source is generally (keep reading!) the most important aspect of an audio system. We build a variety of digital to analog converters (DACs) to further improve your audio source. HeadRoom amps with internal DACs, and our stand-alone DACs, both contain high quality DAC chips in our designs; and, these contemporary high-end digital recievers and DACs are extremely good at reducing or virtually eliminating jitter from the digital bit-stream. Now, here's the exception to our rule about sources being so critical: when constructing a front-end for your stereo system, it is much less important where the digital signal is coming from when a very high-quality DAC is used. We've even found, in fact, that sometimes very expensive CD transports sound only slightly better than the digital output of inexpensive CD players or USB audio outputs from computers when using a good DAC. So, keep that in mind when putting together your rig!"
