Ignoring the now standard (and sensible) GS answer of "what's your room acoustics like - spend your money there first" etc (which is ultimately sage advice)....The 002R isn't the worst interface of all time but its certainly not the best (sounding) one either.. Records have been made with it & as long as you don't want to go higher than PT10, The Black Lion Audio Mods to these workhorse interfaces is definitely worth the price of admission.. I've heard modded and unmodded ones side by side and its night and day difference.. The stock 002 Pre's lose their grey sounding grittyness and become usable indeed..
For the cost of slightly more than the Great River preamp, you could get your 002 Mod'ed & get a "character" preamp like a Black Lion 312 or GAP 73 preamp (Mods available for this too) - which you'd plug into one of the analog line inputs (5-8) as a different flavour.. Going up the money/quality/features ladder - there's several 2 channel preamps out there that each would offer something different to the digidesign preamp... TK Audio DP1 is one very reasonable bit of gear - capable of clean to dirty/vintage sounds.. Then the aforementioned A2D from API... ALso for a bit more, I'd also recommend checking out the Phoenix DRS pre+EQ modules too... a great sounding Pre with some useful channel EQ for sculting stuff on the way in & a KILLER DI- Also..In the same vein is the Aurora Audio GTC2.. never heard one but only heard the love for it...
How many sources do you ever envision simultaneously recording? The Studio i've used with the Mod'ed 002 has a 4 channel API preamp connected to the line inputs 5-8 and the Digital ADAT Input is hooked up to an Audient ASP 008.. Giving 16 Mic Inputs of 3 different flavours to ProTools and is more than capable of recording a live band for a shade over $5k (i'm in the UK so i used ebay to guesstimate the overall cost)..
You might try a mod'ed 002 preamp and be happy with the sound & decide to not even need different preamps - if so happy days and keep on making music with the extra $$$'s in your pocket!!!! That's what i'd do.. YMMV