OK, You're asking me . . . .
Like I said -- surfing. To avoid getting drowned or pulled under, my own practice is to hang back and watch motherboard releases "mature." In fact, I watch forums so that I can see the BIOS revisions mature. This last year -- as I said, switching to picking a "Cadillac" -- I took a big gamble (knowing that it was a gamble) with the Striker Extreme 680i motherboard. I checked reviews, looked for reviews that were benchtest tutorials on over-clocking, looked at customer and enthusiast forums. the enthusiast forums had a different tone than the customer forums, and I deduced a high chance that 50% of the customer-reviews were written by frustrated people who didn't do their homework and didn't know what they were doing. I still think I'm right about that.
Individuals here will point you in specific and narrow directions. And most of them probably know what they're talking about, except for your particular needs. For example-- despite the price-tag and the ambivalent reviews, I chose my Striker board because it had: 8-cycle voltage regulation; three PCI-E slots (including 2 concurrent x16) in specific locations on the board; the Stack-Cool technology and the "heatpipe necklace," and the some 45+ PCI-E lanes.
In your case, price is a limiting factor, but you should look at these other features and see what you can find that meets all the criteria. These days, people are goo-gah about the Intel chipsets, but ASUS and other makers are now selling boards like the P5N with nVidia 750i. You'll have to do the research in these areas -- and ask yourself if you'll EVER want dual GFX SLI, for example.
The P5K Asus boards use a P35 chipsets, and the NewEgg customer-reviews show lackluster acceptance for one variant of the board, with a surging number of reviewers giving 4 and 5 stars to another variant. The X38 and newer chipsets seem to be on more expensive boards -- and I think they are designed exclusively for DDR3 memory -- which is going to cost an arm and a leg right now.
The two makers touted here in this forum recently are ASUS and Gigabyte, with Gigabyte seeming to generate more enthusiasm. I think some of these boards can be found for prices in the $100 +/- X range.
Of course, you could always go with an Intel board. I have suspicions that INtel -- being the CPU-manufacturer -- did a lot of planning to give their boards a long life-cycle -- planning for which nVidia was disadvantaged. But then, the other manufacturers use the Intel chipsets.
Somebody else can chime in here, but I think what you may be looking for is a board with a P35 chipset -- an above-low-end to mid-range motherboard. You might search hard to see if you can get one that has a spec higher than 1,333 FSB, but I suspect that the 1,600 FSB boards are mostly designed for expensive DDR3 memory and the X38 or 48 chipsets.
So price is going to keep you from grabbing the biggest wave as you surf the web for motherboard choices -- it's all a trade-off. You might find the future of the more expensive boards to be longer, but the choices limited by your budget to be shorter.
I guess -- like surfing -- your budget is the quality of your board, and the quality of the board determines the length of your "ride" -- surfboard or motherboard -- take your pick.
On the matter of memory, you'll choose the size of your dual-channel kit according to the operating system you plan to use. If XP, then a 2GB kit; if VISTA, then 4GB. You're better with two sticks in two sockets versus four sticks in four sockets -- some really cheap mobos (like my Gigabyte GA-73VM-S2) are limited to two sockets.
IF you limit the speed of your RAM to modest over-clocks, the tighter latency options will serve you better, so find some memory using Micron D9 parts. Thing is, DDR2 RAM is cheap now, and you save yourself the research-time by buying Crucial modules -- Micron's retail arm. For 4GB kits, G.SKILL has them in various DDR-Mhz flavors. For instance, a 4GB 2x2GB kit of PQ (or PK?) DDR2-1000 modules can be had for about $115. A 2GB kit will cost roughly 60% of that -- off the top of my head.
Last week, I was looking for Crucial Ballistix that were a better match for this Gigabyte mobo and processor, and discovered DDR2-667 Crucial Ball'x at NewEgg for $55 with a $30 mail-in-rebate @ 2 rebates per product per household. ARE YOU KIDDING? SOCH A DEE-ULL, OY-READY!! SOCH A DEE-UULLL!! I bought one at $55, then decided on another, and NewEgg had hopped the price to $58. Today, it's $60-something-plus, with the same rebate.
You can find other brands -- Mushkin, OCZ, A-Data, etc. and they make some of their modules with the Micron D9's, but you'd better have a close look at that online database of memory brands and models as you browse the resellers. And -- sorry -- I don't have that link at my fingertips at the moment.