Ok, according to the chart I posted (the link) the Pentium 4 2.60GHz is a little bit better than yours, and the Pentium 4 2.40GHz is a little bit worse.
Prices are (taken from geek.pricegrabber.com):
Pentium 4 2.60GHz = lowest is $110.95
Your Sempron 3300+ = lowest is $103.00
Pentium 4 2.40GHz = I could only find one seller,
and it was $179.00! puke:
Dunno what to say about that...
Hope this helps.