Nope. Not the same instrument at all. Although I'm in line for the initial shipment to Sweetwater at this point, having both a 2600 and 2500 side by side at one point was really revealing. The 2600 works like pretty much any other patchable from this period (such as the EML 101) and was designed to take on the Minimoog. Very straightforward architecture...3 VCOs, LP VCF, etc.
The 2500, though...that thing is the "OG 0-Coast". It has filters...AND LPGs in the form of the Filtamp. Then there's that Mixsequencer...sheer brilliance, and key to a lot of the 2500's mojo. And on and on with the divergent architecture, which was presumably to position it as the "Moog alternative", but which also made it pretty unique...there's not really been a lot of stuff since it came out that replicates what a 2500 can pull off. Plus, the matrix switch setup, though buggy and prone to crosstalk if you didn't keep the contacts in the sliders clean, allowed routings that were simply not capable on anything at the time; it would be a few years later, when Serge Tcherepnin cooked up his system, that you had that same "route it to everything" sort of capability.
There's definitely reasons why those 2500 main and wing cabs go for prices that rival the GDP of some third-world countries on the used market!
