That seems pretty OK to me. Add some latency for the hardware to get the MIDI into the computer, it should still be equal to being 4-5 feet away from the source, which is less space than you have to your fellow musicians in a rehearsing room.
I haven’t used ESI products in a long time but when I had a PCI audio interface of theirs many years ago, it was the most stable and low latency solution I could get at that point for my PC, before I moved to Mac and Pro Tools TDM.
Whether it will give you a significant improvement or not, only you can tell by trying it out. My personal guess is that you will notice a difference but not a significant one.
