As far as outboard gear I'm using a 1960 Drawmer and an avalon VT74SP, both class A tube compressors. But truthfully I rarely use them anymore for mastering unless the original material is "brittle" like what folks sometimes end up with if they use old 16bit digital gear (VS880/1680 etc.). I pretty much use software now and it's not so expensive - $600 will get you good mastering software from Sonic Foundry, Stienberg, Pro Tools etc. A couple of hundred more for plug-ins, mabey $500-$1000 for some really good DACS, a couple sets of monitors and your in business. The real tricks to mastering is a good ear, experience, decent source material, and a monitoring environment that translates well to consumer speakers. When I pre master for an artist (or myself) I take the following steps.
1. Transfer the source material to computer. (This is why you need good converters)
2. Adjust volume only (No compression yet) so channel levels match.
3. Hiss or noise removal. If the track is very noisy, I will do this in two or three passes which seems to preserve the source material better than trying to cut out all the noise in one pass. Note that hiss removal software can also kill some of your reverb tails if you apply too much, but you can use this as a work around for music with too much reverb as well.
4. Click, pop, and glitch removal.
5. EQ (It's important at this point to make sure you can hear all the elements of the mix at extremely low volume levels. It is equally important that it dosent sound too bright at high volume levels.
6. Time to take a listen through headphones too. Excess fx processing is really noticable through headphones.
7. Apply reverb, sonic enhancement etc...go light because this is the seasoning not the meal.
8. Compression / Volume maximizing. This is critical because it's easy to overdo, underdo. Compression can be hard to hear until it's way overdone
9. To get these steps right you need to be able to jump from track to track as you listen to make sure they all match in terms of EQ volume etc. You also need to switch between at least two different sets of monitors. (I actually use 4 - A multimedia set for PC, high-end studio monitors, Auratones, and your garden variety home speakers. At this point your music should sound out at the same level, eq, etc...as your favorite CD mixed by the fat cats with a jazillion dollars to spend on production.
10. Resample to 44.1k
11. Cut a red - book compliant CDR or DAT for the artist.
12. Get paid - then turn over the goods
13. Go to the %*%&ing bank!
The cost of good mastering tools are nowdays low enough that anyone with desire can save up enough money to own them. The deal is - paint brushes are 2 for a dollar but some people will become house painters and some become picasso's...
Peace
Dan