I would wait 60 days. AMD is about to release Socket AM+3. When they do, the i7 series (mainly 720) and supporting motherboards may drop in price. It would be dandy to build a i7 720 for maybe a tad more than you will build a E8400. If there is just a small difference it may be worth the wait. Currently the E8400 is $165. The i7 720 can be bought for $240 which is $85 more but you will have to invest in a more expensive supporting motherboard and DDR3. I don't see it being close to the price quotes on the rigs in this thread but you may see more drops in all Intel products after the release.
There is no 720 i7 processor. There is a 920 and they can be had for 230.00 (nor distributor prices) the E8400 can be had for 140.00 (not distributor prices). The i7 will not drop in price. Intel drops prices two times a year at most. Vendors may get rebates to them from Intel and pass the savings onto the consumer at their discretion. The next price drop for Intel will most likely be when they release i5 processors (sometime in the 3rd quarter if they name them i5) which will be in line with AMD pricing but out perform them. Not all processors across the board get price drops with Intel only a select few. I would not expect to see the 920 drop anymore then it is at now. Motherboard maybe a different story, a few new boards are slated for release, but again, the pricing will remain stable on the current boards. The best entry level X58 board out there is the P6T from ASUS (249.99). It has almost unlimited overclocking, the native memory is 2000, 1866, 1800, 1600, 1333 and 1066. I have this board with a 920 at 4.4 and some special OCZ memory running at 2800MHz 24/7 on the P6T. THis is not the Deluxe board just P6T the P6T Deluxe wont do what this board does. If you choose to go SLI with this board and using the NVIDIA (any flavor GPU) you have to get the drivers from nvidia.com. The drivers on the GPU disk will not work to make the SLI available. Same thing for most of the x58 chipset motherboards and using nvidia graphics cards. Just a suggestion to the poster if your going to go i7