Hi there,
I recently asked the most successful producer that I know (Mack Damon - 5x Grammy nominated....) a fairly similar question and the following is a snip from the message he sent me in response:
"I'd recommend heading over to vintage king and checking out the 500 series pre/eq's and getting a 6 slot rack. This allows you to add pre's one at a time for about $750. With pres it's all about colors. You could have 1 API 512C (the API everyone has to have at least 2 of), one purple audio pre, 1 neve, 1 a-designs, a shadow hills GAMA pre (I'm buying the 4 channel next month...platinum producers say it's the new holy grail). This is initially expensive for the first channel, but it will allow you to grow cheaply and get the multitude of tones you want. You want to record ALL GUITARS through the API. The purple pre will be a great vocal pre with a ton of character, the purple compressor fits in the rack as well, and if you record vocals through it, everything gets a 1000% upgrade."
I don't think it's fair to be selfish with advice like this....hope it helps you as much as it has helped me!
edit: Forgot to put a link: http://vintageking.com/Shop-New-Categories/500-Series
They have a deal where you buy any 4 modules and get the API 500B6 6 Slot Lunchbox for free....not a bad deal at all!