Studio Mixing Boards
If you're currently recording on your computer at home without an external mixing board then the biggest move you can make is to integrate a mixing board into your set up. The difference in sound will knock your socks off! Something about taking your recorded audio outside through an exterior mixer that adds another depth to it that's really quite noticable.
Even if you're using a high end recording program like Pro Tools and you've been mixing on it's virtual mixing window with all sorts of plug-ins, you've got to take the next step and route it all through an exterior mixing board... it's like someone just let it out of a box.
Like most other pieces of gear these days you can get in for under a few hundred dollars and go up into the 1000's with several choices like analog or digital mixers, number of channels, mono and stereo, number of submixes, onboard effects, powered, studio or live etc.
Behringer Powered Mixing Boards
Probably the biggest bang for your buck is Behringer. A German company that's international now and make all kinds of musical products. Their mixing boards are well made, simple to use, very reliable and they have a model for almost every application you may need.
24 Track Analog Mixing Boards
Ahh... the 24 track analog mixing board, still the preffered standard in most music recording studios, and for good reason.
Yamaha Mixing Boards