I've seen both MP and Xeons from that performance range (2.0Ghz to 2.4Ghz) operating. They're already kind of old-gen, but make for good systems nonetheless.
You might, however, be troubled when trying to find a good chipset for the MPs. That was, BTW, the main problem with those: bad feature sets and rather inefficient chipsets plagued the MP systems. They are, however, probably still considerably cheaper than comparable Xeon systems. Xeon systems, BTW, all have HT enabled, which might help a little in server jobs.
So basically, my advice: try getting two comparable offers with the same budget, but keep in mind that Xeon systems from that time will probably be more suitable for your tasks, mainly because of the chipsets and a bit because of HT. Then compare them objectively... If at the same clock, pick Xeon over MP. But...
And I couldn't resist suggesting...
Are you absolutely sure you can't afford a dual opteron system? Even one with, say 240/242/244 Opterons? Keep the prices in mind:
240 (1.4Ghz) - US$123
242 (1.6Ghz) - US$158
<i>Athlon MP 2200+ - US$164 (your choice)</i>
244 (1.8Ghz) - US$203
246 (2.0Ghz) - US$307
Consider that an Athlon MP 2200 will cost you US$164 and will probably get its ass k!cked royally by the dual 242 system. And also, CS servers probably also get a 64-bit enabled bonus. And Opteron chipsets are much better than the old MP crap you'd probably have to swallow...
So my advice to you would be: try and get Opteron if you can. It's the best bang for buck, it's current tech, and it is, without a doubt, the processor that will suit your needs.
I'll check later and post the link for a CS server benchmark. Opteron truly shines in that...