Ok, let's confuse Mophro a bit more, or maybe help him.
General thought: the system you want to build has nothing "high-end critical", so you have a lot more choice and you can even compromise (for example, pick the case you like the most aesthetically.)
Computer cases: both will do the job. Each one has small advantages over the other one, nothing important.
Washable air filters for Antec, or (almost?) tool-free assembly for Cooler Master? Two large exhaust fans close to each other for Antec each one with 3 speeds selector and an extremely open perforated front bezel, or one large exhaust fan and a smaller intake fan but placed on the opposite side (more logical) for Cooler Master? But also more optional fans for Antec? Front panel connectors at the top for Antec, at the feet of the case for CM? (Which is the more convenient for you?!) Etc.
It's your pick in the end. What you like the most.
PSU: both will do the job too. Both Antec and CM are serious companies. Personally, I dislike when manufacturers invest in the look of PSUs because it's less money for what's inside, but, hell, they are all going to do that now even Antec. The CM looks well designed, modular cables are handy, and they claim it's a "silent" series (and Lupus seems to confirm) while the Antec doesn't belong to the "silent" series of the manufacturer. It delivers less power than the Antec but it seems it's more pleasant to use. So maybe it's your choice, and you can install it in ANY of the two cases. It will work. So an Antech case + a CM PSU is possible. (As well as the opposite.)
Graphic cards: both will work well. Probably slightly faster for the 250-based one for some things, or you save some bucks with the 9800-based one.
But Core is right: at the moment, ATI offers the best cards in almost all the situations. The problem with AO and ATI is that AO is still (and until the new engine) based on an old implementation of DirectX 7 and Nvidia supports DirectX7 a bit better than ATI.
This is the reason why we went for Nvidia BUT it's because I don't know how the current ATI cards run with AO! Playing safe here, that's all. If the current ATI models run well with AO, then no reason for getting Nvidia. But I don't know.
RAM: you mention only 2GB for my suggestion but I put 4GB in my last proposal and so did Lupus. Anyhow, 2 GB is what you NEED today to be comfortable on a home machine. You don't strictly need 4GB unless you run RAM-intensive applications or a lot of simultaneous applications. But, indeed, 4GB is nice to have, and gives you room. (Of course, high-end specialized applications now easily require up to 12GB and more on PCs.)
Conclusion: what you want, and 4GB if you can.
DVD/CD: the OEM Samsung will work OK. No need to worry about anything else for this class of system.
Hard drive(s): here, Lupus and I will always be on different planets I guess

He likes RAD 0 to increase HD speed by splitting data and write/read operations over 2 disks. I dislike the solution because it multiplies by 2 the risk of disk failure, and data will be harder to recover in this case. If you go for RAID 0, at least make sure you invest in a good backup system so I can sleep!

(Yes, I'm a very stressed person.) Side note: RAID performance also depends on the RAID controller.
Conclusion: your pick really.
CPU and MB: both solutions are good.
- Intel Core i5 on 1156 socket:
- faster indeed
more expensive
not much CPU upgrade possibilities in the very near future and after like 3 years without changing the MB; on the other hand, around 2 years, the already existing CPUs for the 1156 socket should be cheaper and offer good upgrade possibilities, plus a few new CPUs likely
AMD on AMD3 socket
- less expensive
less fast but still pretty good
relatively better quality/price ratio
wider upgrade possibilities for the CPU
Note: this is about CPU-only upgrades. Most future improvements in PCs will required to change MBs.
Good luck!
