From what I can tell, the problem is going to be if the BIOS supports it or not. But yes, the Pentium E6500 (2C/2T) is technically more powerful than the Core 2 Duo E6600 (2C/2T): the Core 2 uses the Conroe (65nm) architecture, the Pentium uses the slightly newer Wolfdale-3m (45nm) architecture. The Core 2 is slower per core, hence why it's a step down in the hierarchy (https://www.tomshardware.com/reviews/cpu-hierarchy,4312.html).
Assuming it's compatible with the BIOS, & assuming it's limited to the 65W CPUs, your best bet might be the Core 2 Duo E7600: slightly faster than the Pentium, more L2 cache, & 2 tiers up.