I got my 2500+ yesterday so I haven't had time to do much testing yet, but the main bottleneck in my system is the memory. I'm running 2x512MB TwinMOS PC2700 CAS2.5, but they report no errors in Memtest86 when clocked at 2-2-3-7 at 360MHz. This was faster than 2-2-3-6, which also worked fine, btw.
Regarding the CPU I could bump the multiplier to 12.5 (x180) with no vcore change and very modest cooling. It stayed well below 50 degrees celcius even with full CPU load for hours. However, prime95 gave errors after about an hour and upping the vcore to 1.75 didn't fix it. I think this might have to do with memory, so right now I'm running stress testing with 175x12.5 (giving 45 degrees celcius for the CPU under load). If it works ok I'll give 175x13 a shot, but that is 2275MHz and without a vcore change it'll most likely give errors right away. I'll probably stay at 175x12.5 but with a lower CPU fan speed (thank you
SpeedFan) to get the system as quiet as possible.
And btw, my 2500+ was completely unlocked and I can access ALL multipliers (even above 12.5). I'm using an A7N8X Deluxe with the 1003 BIOS.
I'll probably make a post with more extensive testing results and system specs in a few days.
EDIT 5 MINUTES LATER: No I can NOT use the multipliers above 12.5 it seems. I can select them allright but they work as with other Athlon XPs: 13 gives x5, 13.5 gives x5.5 and so forth. I guess the unlocking has to be done in hardware after all.