You don't say how many channels you want to expand to, but I really think that you should consider carefully what you want to achieve before you spend any money on a mixer to go in front of the DP01. The Tascam DP01(FX) is a 2-channel unit with up to 8 tracks storable plus transfer to a computer. If your way of working is to capture the tracks, mix in the DP01 and then transfer them to a computer for CD burning, I would suggest that you would get better results with a multi-channel interface connected directly to the computer, by-passing the DP01. By using a low-cost computer program such as Reaper, you would get much more functionality than is available in the Tascam DP01.

Even the 8-channel Tascam US-1800 at under $200, while not a high-quality unit would nevertheless give you better results than a cheap live sound mixer run through the DP01.

I used a Tascam US-1641 (previous model before US-1800) and got some decent tracks. It's all about how you mic the instruments and how you tune. Your end results are gonna be effected by how good the raw recording is.

As far as mixers go and reliable gear, I've been using an Alesis USB board for 4 years and it hasn't failed me yet. Just upgraded to a Multimix USB 2.0 which has 16 inputs. Works fine with Audition CS5.5 and Logic 9.

A CHEAP mixer may degrade your sound quality, do research on room treatment first.