Hmmm it still doesn't seem right that 4xMSAA would cause stuttering if you aren't using any texture mods. The official hires pack shouldn't make that much of a difference. If you want to know for sure, download MSI Afterburner and setup the on screen display to show you GPU usage, temp, FPS, and VRAM usage. It's possible 4xMSAA was giving you stutters from poor performance, although unlikely given your GPUs. V-Sync would be the culprit there if that is somehow the case. An SLI setup will also increase heat a lot, possibly enough that your card could be throttling, which would need to be fixed ASAP. Basically, MSI Afterburner is a great tool for identifying problems due to hardware shortcomings.