Mid-priced warm sounding DAC?


I've recently decided that a good route for me to take is upgrading my system with a good DAC. My current system is a bit bright sounding, so I'm looking for a good DAC costing up to $600 (used) that will provide a smooth, warm sound to match my currently bright system. I'd also like the DAC to be capable of upsampling, although if necessary I could add an upsampler to the digital chain at a later time. My preference would be to have it built-in, however.

Any suggestions?
jwglista
Another non-upsampling DAC to consider (even though you didn't say you are looking for one) is the Poth Audio:

http://www.pothaudio.com/prod.php?view=20

Really quite an impressive sounding unit and a steal for the price.
Mezzrow, do you own the Poth Audio Dac? Can you tell us more about it's sound.

Dave
Thanks everyone for the input. I'm still unsure as to whether or not I "need" upsampling. I've read that upsampling can somehow push distortion up above the 30 kHz range, but I have no idea how that works. Also, some of those tube DACS only have a 16-bit D/A converter. Wouldn't I want at least 24/96 ?

That Poth Audio is extremely cheap, and is something I could purchase right now. But would it be worth it to just wait? I'm sure the DAC in my NAD T 513 DVD player may be equal with the Poth, which would make it pointless to purchase this.
I think that all the advice to check out the non-oversampling dacs is right on the money. I have a Shigaraki DAC and it is filterless and non-oversampling and I run it with a battery. It is SMOOTH and MUSICAL and just right.........like porridge.
Buy a quality USED DtoA converter. There are a lot of them out there as people have been buying single box units.