You took care of yourself last??? That's the most important one, gotta let the Big Dog eat.
Its not a bad deal, no. But its not the best deal IMO either. It depends on what you will be using your rig for and if you plan on overclocking. The Barton's extra L2 is beneficial in limited apps, most noticeably office apps and games (due to predictable cache accesses). Non-predictable and non-recurring operations like multimedia work benefit from clockspeed. Equally clocked Barton's vs. T-bred B's see a difference of at most 5-10% in apps (from various review sites) where the extra L2 is beneficial. In this case, a 2400+ will have a 167MHz clockspeed advantage over a 2500+, so I'm pretty sure it would beat or tie the 1.83GHz clocked 2500+ in just about every benchmark. If you are overclocking, the results would be similar as Barton 2500+ seem to hit in the 2.1 to 2.2GHz ranged whereas the T-bred B 2100+ or 2400+ accomplish 2.2-2.4GHz. Factoring in the price differences for relatively equal performance, it would be hard to justify paying almost 2x as much for the 2100+ or $40 more than the 2400+ when you going to see similar performance at stock or overclocked speeds.
It really depends again what you plan to do with your rig. Yes, there's dual-channel DDR to consider, but the performance increases are rather insignificant the majority of the time, and even in apps where there is a difference, its not much (5% max). If you think you may want 1GB of RAM in the near future (say 3-6months), I'd say buy 1 stick of 512MB now, and pick one up later for dual-channel DDR. Otherwise you'll end up eating depreciation on 2x256MB modules, which will devalue faster as mfgs. and consumers begin focusing on 512MB dimms. Then you'll have to pony up for 2 x 512MB. Could get expensive. Theoretically, you could still get dual-channel by using 2 x 256MB in slot 1 and 2 and 1 x 512MB in slot 3, but I've read of a few problems and don't totally trust that configuration. It will also be detrimental to any OC'ing efforts as the nForce2 memory controllers can be a bit touchy; each dimm you introduce increases the chance of instability and lower FSB OC'ing headroom.
I'd go with DDR 400 if you are buying new RAM. I'm using XMS 3200LL and its been great. Even if you get a 266MHz XP, you can adjust the multipliers and FSB to run stock speeds w/out actually overclocking the processor; faster RAM will give you the flexibility and headroom to accomplish this. Also, AMD will soon be releasing their 400MHz FSB chips, so PC3200 will be natively able to support these new chips in the future.
Np. Once you put enough systems together, the info I passed along will come as 2nd nature. There's always a slight learning curve with each new board/chipset generation, but for the most part, motherboard tweaks/troubleshooting hasn't changed relative to its predecessor since softBIOS' have been released.
I'd check out:
Googlegear as a reference point; they're typically the price leaders of the better regarded e-tailers when it comes to RAM.
Monarch is excellent as well, and they're on the East Coast; I bought mine from there as they were cheapest at the time.
And of course there's Newegg, but I've found their RAM prices tend to lag behind the others.
Essential Computers (essencompu.com) is another excellent e-tailer I've used in the past. All of them are excellent when it comes to quality and service, and offer cheap ($2 or less) or free shipping as well. Definitely go TwinX if you want to go dual-channel as there isn't any price premium over 2 separate sticks of LL, and you get the protection of being able to RMA w/out question if they don't run at their rated speed and timings in dual-channel.
Chiz
Edit: Post #200 :beer: I had post #100 too.