I'm sorry for being not too explicit in my replies.
As far as I remember, Mushkin did not have any software to measure memory temperature, so I guess you're reading it from heatspreaders via probe or infrared sensor, right? If so, then 49c just shows that HS are doing the job of absorbing heat from the ICs rather well and if you want that temp to be closer to ambient then airflow is the way to go.
Given that memory produces at most 20W of heat across the area of 32 ICs I don't think that default thermal pads are anywhere near their limit hence are in no need of replacement. Of course, perfectionist like yourself might think differently
I appreciate your enthusiasm in the idea of 4x2Gb of PSC for daily use. What I was trying to say in my post is that 4x2Gb configuration will be a lot more difficult to stabilise compared to 2x2Gb, in most cases you will be far from what individual kits/modules can achieve. Given that your current 1200MHz CL8 1.75V overclock doesn't provide too much headroom, most likely you will have to back out either in timings (to CL9) or in frequency (to 1100MHz), this is why I think 4x2Gb is not going to work out in your case.
Also, you say that 2x2Gb of PSC costs $20. Yes, but you have to be very lucky for it to be stable at 1200c8 with 1.75 or less at this price, I can't remember more than 3-4 such cases in my two years of binning.
tRCD and TRP are still very loose for 1200 and Samsung, have you tried lowering those?
Also, I don't think if 1.2Vccsa is strictly necessary for 3570K to do 1200MHz mem, unless you have a sample with bad IMC which happens to scale from Vccsa so well.
Your "keepers" make my 4 kits look like Spartans
Will be interesting to see how your 2300C8 do. The experience and feedback I had so far was not very convincing.