MPC 3000 set up help

What's good yall I did my homework on a lot of this stuff but still undecided on some small things.

All I have at the moment is an MP3k and a pc with a basic PCI sound blaster audigy crap sound-card. I track out beats into Adobe audition sometimes via a line in which equals mediocre recording quality at best into the PC. I can't describe what it is but let's say I don't track out one by one but just record a single stereo mix of the whole beat into the daw it sounds like something is missing when playing back it doesn't quite hit the same as coming from mpc. Any meaning to this? Or is that just the way it is?
next few upgrades I want to get has to do with improving sound quality and clarity of my mixes and was thinking either a hardware mixer to and also a new interface at least with two mic pres. Which should I get first to get most improvement to sound? Should I get both even? What other options or recommendations as far as outboard gear? (Compressors, whatever ). Thanks

Likely it is the crappy sound card, or if it's really off, bad cable...Im leaning towards shotty audio card though...

You can add a mixer between mpc and your audio interface, however you can aslo achieve EQ in software you'll be tracking out to.

If you can get one piece at a time, go for better audio interface...

Cool, so getting another interface first would be better. add mix board afterwards

I understand the mixing capabilities of a given DAW but I want a board also because I'm still trying to develop a type of sound and I want to see how good a sound I can get with it recording live