if you have a Q9650, you dont wanna get anything less than a TRUE or a megahalems. i would honestly go for the new venomous-X from thermalright though if you want to stick to air. my Q9650 wouldnt run linpack at all with the specs in my sig, it would immediately hit 80c and then thermal shutdown would kick in a second later. im water cooling it now but i was running it OCCT 24hr stable under a megahalems with those settings. temps under occt were in the 65-70c range on an average day (72f ambient), tends to get a lot hotter here though in the summer.
ed: if you cant fit any of those tower coolers in the antec solo, i would consider looking at the corsair H50 as an alternative, and putting push/pull fans onto it. its a reasonably good performer, nothing like a DIY water cooling setup but it performs alongside the best of the air coolers. comes with shin etsu thermal grease preapplied as well, so aside from swapping out the fans its ready to go out of the box