What client are you using? I have had good luck with the new v7 client, which they've been adding some features to as time goes on, such as improving the PPD estimates and showing overall PPD as well as per-'slot' PPD. I run in Expert mode to get extra info, so I'm less familiar with how much is displayed in the other modes.
My home server (folds 24/7 but also hosts two virtual machines and handles HDTV recording and transcoding) is a Core 2 Quad Q9300 (@ 3GHz) running smp:4 which nets ~5k PPD, and a GTX 650 Ti (Core @ 1019MHz, RAM stock, using the relatively recent but not brand new 310.70 drivers) which is getting ~17.6k PPD
So I'm getting ~22600 PPD on a lesser machine under ideal conditions, and it will vary depending on the WUs I pull down, how many TV recordings are scheduled, and if I use the box myself to play games in my basement when wife and/or kid are asleep
I believe SMP benefits some (not a ton, but it is noticeable) from having Hyper-threading enabled, so if you're currently running smp:4 with HT turned off, you could turn it on and run smp:8 instead.
Also, do you have a passkey configured, and is it 'qualified' for QRB (quick return bonus) points? If not, you might be getting nearly 22k PPD from your GTX 660 alone and only getting the (much lower) base points for SMP WUs. I feel like you should be clearing >10k PPD with an i7 3820 running smp:8 with a qualified passkey, which would push your total PPD for that machine into the 30k+ range (again, depends on the WUs/projects that get assigned, and how much gaming or other workload you put on the machine outside of just folding)
And welcome back!