Back to topic... can you more experienced "mixers" offer any suggestions after I lay this out?

First of all, I decided to buy a desktop to run BIAB so I can put an actual sound card in and not use a mic in to record back to the laptop. Now, what am I recording?

I run my BIAB feed through my mixer with a 31 band and a digital reverb looped in. That goes to a Tascam direct to disc 8 track recorder. BIAB goes on track 1. Manual keyboard on 2, vocals on 3, drum fills off a drum machine on 4, harmony vocals on 5, the other 3 channels are for solos.

I feed that out of the Tascam into the mic in on my laptop, running Goldwave. When I listen to the tracks in headphones, they sound fine. In my Wharfedale monitors (which I strongly recommend, btw), they sound fine. When I play back the newly created mp3, it is really muddy, very midrange dominant.

Now, with a desktop and a sound card with RCA ins, I can send that Tascam feed back through the 31 band EQ and tweak it again.

So I think my question becomes, is it the conversion from wav to mp3 that is killing my fidelity? I save them at 320 rather than 128 for as high of a sample rate as I can get. Big files, but who cares?

Any ideas?