That's got to be your decision. There's a good comparative review of Intel and AMD performance/price on this site. It doesn't show any AMD chips slower than 900 MHz., but you'll get an idea of the performance difference that 50, 100, etc. MHz. can make.
$41.00 (USD) for 5% performance is a good deal in my book. Plus you might extend that margin if your into overclocking, but thats more $ for cooling solutions.
Faster chip = 6 additional months till next upgrade.
wrong, 5% for $41, why not just save few dollars, an OC it.
you'll get the same result with a 800 or 900. they aren't going any higher than 1.1Ghz, another suggestion, look and ask around for a blue BIRD, you pay a little more, and you get more.