AMD Athlon 64 3400+ or XP 2500+?

Hi eveyrone,
I cant make up my mind as to which CPU and M/Board to buy. Im currently going for a AMD Athlon XP 2500+, and a Gigabyte K7 TRITON GA-7VM400M. I read that the AMD Athlon 64 3400+ is only 2.18Ghz, same as XP2800+, but someone recently told me that the (xxxx)+ is equivelent to Intel speeds (eg. 2500+ = 2.5ghz) Is this true? and if so would you reccomend buying Windows XP 64bit and a AMD Athlon 64?

Thanks in advance.

PS: Addition Specs are:

512MB/1024MB DDR 333Mhz/400Mhz RAM
Lite-On 16 DVD-ROM
Lite-On 8X -/+ DVD-R(W)
Western Digital Raptor 74Gb 10000rpm SATA
Hercules 3D Prophet 9800 Pro
Creative Sound Blaster Live 5.1

If you aren't concerned about cost, the 3400+ 64 will blow the 2500+ xp away in terms of performance. There is much more to cpu performance than just the clock speed, which is why Intel is using a new naming system for its chips now instead of just "2.8 ghz". The 3400+ 64 will need a different mobo (I'm sure you knew that, but just in case), and will cost quite a bit more, but it will scream. You don't need windows 64bit, the athlon 64's run 32bit apps just fine, with a slight performance increase (which is why they are so good.) Anyway, 64bit windows doesn't work all that great. Don't bother.
If the cost is a factor though, the 2500+ is a good cpu, and overclocks pretty well. It would work just fine for all current games and applications.
HTH