Rebate is actually $35, not $25.

I got 2 sets of these and they are ok but I am now ordering some 8500 sticks. Mine are good to about 880mhz but no more. And that is with 2.3v. They fail over 880 in Orthos with my E8400 setup. If you are looking for 1000 these may not be for you.

Are you running all 4 sticks when OC? If so, you should try just one pair at a time to see max overclock.

#3, why would that matter to #2? If he's got 4 sticks, he's not going to put two on the side just to find out his max theoretical OC. I guess there's a chance one of the sticks is bad, but it doesn't sound that way.

4 sticks are harder to overclock than 2. Memory controller can't keep up and may require more voltage to handle.
So maybe it isn't the RAM that is his limitation. It could be his OC ability or the MotherBoard. Of course it could also be the RAM.
I have bought close to a dozen of these 6400 ballistix. I haven't maxed them all out, but the 4 or 5 I did would easily reach 1000mhz at 5 15 timings. I love the Ballistix line. I have a set of OCZ reapers that won't OC much. I also have a set of 6400 Mushikins that OC pretty good (about 950mhz).

Yah, if you want 4GB, don't get these. Go for a 2x2GB kit instead. I'm pretty sure these will reach DDR2-1000 if he was only using one kit. He may need to raise his MCH voltage, too. I have four of these kits as well, and they all reach DDR2-1000 at least, when only using 2 sticks at a time.

I have 4x1 GB Ballistix Tracer PC-8500, and they work fine on mine 2.2 volts, DDR2-1066 5-15, so the ratings do matter most of the time.

I D9-GMH chips, and i've heard they've since changed to GMK chips which don't perform as well. The D9's have gone the way of the BH-5's and TCCD's.