I don't know that unit, but I *think* you'll have to spend some $$ to notice a real improvement over it. If drums are your main instrument, then you're maybe in the most demanding subset of us folks when it comes to the signal chain
I'm new to recording drums (and generally don't know what I'm doing, so keep that in mind) - so far, I like cleaner sounding preamps for the overhead mics - (I think I'd be satisfied with the Onyx ones) and other ones for the close mics.
When you compare your drum tracks to others, is there anything you wish were different about yours? Assuming your drums and cymbals sound the way you want them to in the room (well tuned, heads in good shape, etc.) It may be that the better place to spend money would be on mics, for instance. I'm not familiar with that drum mic kit, but I suppose you're using the I5 for the snare, and a specialized kick mic for the kick, but what are the overheads? F something? That might be what I'd look to replace first, if anything. edit: -- looked it up
ADX51? I admit I've never even seen one of those, so I'll just be quiet now
Anyway, the preamp I've been using for most of my close mics is the API 3124+ - used, and on a per channel basis, it's in your price range
- I attenuate the outputs and then I crank the gain, and it sounds way better than is appropriate for my level of playing. I'm thinking about getting another one so I'll have 8 channels. For my overheads, I've been using a Great River MP-2NV, but I try to run it as clean as I can, so I don't really use the "character" of it. For my kick and sometimes my snare, I've been using these ACMP preamps we got here in a group buy a while back - they're chinese Neve "inspired", and I think the closest commercially available preamp would be the Golden Age Project 73 (GAP 73). For mics, I'm using Oktava MC-012s for the overheads, Sennheiser MD421s for toms, and MD441 (or sometimes Audix I5, or modified Shure SM57) for snare top, Shure SM81 for snare bottom, and AKG D112 for kick. Not that I'm recommending these (except the MC-012s for overheads - I recommend those, and I'm definitely happy with the others), just disclosing.