I had one that I bought almost new (the first owner returned it to the store because it was too much amp for what he needed) I got it for a good price.
It had loads of reserve power. I used it to drive 2-1X15 cabs and ran it bridged mono at 4 ohms. It was way more power than I needed too and even though I had it mounted in a lightweight SKB 4 space rack, it was more weight than I was willing to haul around.
Other than that, it sounded like any good GK amp. Previously I had a 400 RB that I used for 10 years. The 2000 had the same sound but more solid bottom end at higher volume. Great for outdoor gigs where the 400 would be straining a bit.
I had no problems with it and sold it for a decent price when I decided I didn't need all that power and actually wanted something lighter.
If the one you're thinking of is a good price and is trouble free, then I'd say get it if you actually need the power. The advantage with the 1001 RB is lighter weight, plenty of power for almost anything except driving very inefficient cabinets and a factory warranty.
Others here can tell you more about the 2000 and how to upgrade them if needed.