You're right... my Q6600 will run 5, and with the slaves on med-low settings it is fairly smooth. Nothing great, but playable. The biggest problem I had was one or two toons would drop follow quite frequently while grinding in Elwynn Forest/Eversong Woods (I tried both sides on different realms). A couple of things that came to mind were that instances and major cities would be frustrating to no end, and that my setup would be far from future-proof since there's the likelihood it would become less playable in future patches. Would a higher end vid card resolve this? Possibly. A friend let me borrow his 2GB 4850X2 for a weekend before I'd decided to build the second rig and I seen a little improvement after testing a variety of configurtions to see what worked best. Cities were still choppy as predicted, Orgrimmar and Stormwind were like a slideshow near the bank/AH. A 4870 might have been a bit better. /shrug Had I tried running 5 on a single monitor it could have been smoother than on two. For me, squishing 5 toons onto either a 19" 4:3 or a 20" widescreen just makes the windows too small to be playable. For that matter, running 5 on those two monitors made the text and portrait healthbars too small to be useful for me. 3-boxing on those 2 monitors with the 20" roatated in portrait mode was ideal for my eyesight (which isnt horrible btw) and kept up really well in all the areas I'd travelled. It only seemed logical to get another 20" and complete the H-configuration to make the move up to 5-boxing.

I was considering adding SSDs, sym-linking, and so on. The potential expense of staying with one machine was escalating with every "what's next if this doesn't help enough" thought that crossed my mind. The option of multiple pcs seemed a less costly choice all the time and I didn't want to potentially fall into the routine of chasing down the FOTW video card or other bottleneck cure every few months to keep up with new content, only to see it all get hit by the failtruck should a new expansion come out in the next year. I want to believe that will be 18 months down the road, but nothing is certain.

What settled the score for me was reading posts on here. Some 5-boxers had come to the conclusion their Q6600s had seen its day, but just wasn't cutting it anymore. Then I read posts from other members (mikekim, vyndree and pinotnoir in particular - thanks so much for all the info you all shared) that highly praised the use of multiple pcs over a single one and how much smoother it becomes splitting the load over more than one machine. It couldn't have been more accurately described. After the upgrade to the Q6600 and donating parts to the alt rig, playing the 5 toons spread across two machines is so smooth it "feels" more like youre only dual-boxing again (logically) while using med-high graphics settings.

I would recommend leaning toward the 2nd PC, especially so if you have some of the spare parts already. It's slick, and much more future-proof.