wait for IVY bridge. It is better in every which way. By than the first kepler cards(nvidia) will be out and about. The pricing war will start on GPU's and you will be very happy. I would watch slickdeals/techbargains etc etc and get your base components at good prices. SSD boot drive, PSU, case, Cooling , and memory. Not much chance in RAm dropping in price any further in that time frame. With the money you will save you should be able to get yourself a much better system than buying all the components in a days time.
I've already decided to get a Kepler when they come out in April/May, but what i really want to know is if the extra performance of Ivy over Sandy at launch will warrant the higher price tag at launch, since Sandy will be considered "outdated", they will be available at discounted pricing, where as Ivy should be roughly $20-30 more with questionable stock available. But seeing the new leaked benchmarks, it seems as though Ivy will be roughly 10% faster than Sandy in terms of CPU while maintaining a lower TDP. And with Tri-Gate implementation i can only presume that with more extreme overclocks, the need of voltage won't be as extreme
I understand your concerns. 3d transistors is more than enough to take my money. Yes ivy might not be the best buy but it will be "cool". IT all depends on how much money you want to spend. sandy B is more than enough for just about any application a normal consumer will do for the next 2-3 years.
I would just do as I previously recomended and score some good deals until april rolls around.
Ivy Bridge CPUs should retail for around what Sandy Bridge is currently selling (maybe $5 more). Of course if demand outstrips supply, then retailers and e-tailers may charge a markup (Intel has nothing to do with any markups).
The flip side is that you might see a lot of used Sandy Bridge CPUs selling fairly cheaply on ebay. Of course if you are interested in an i5-2500k, then the one thing to take into consideration is have much has it been overclocked and if the default voltage was increased for the overclock. I expect retail Sandy Bridge CPUs would sell for around $210 - $215; just a small drop to make room for Ivy Bridge. If that's the case, then I probably would not want to pay more than $160 for a used i5-2500k.