Well this is a huge area encompassing both the system ram and also the disk. Right now it feels like going solid state on everything is the way to go, so we are thinking just get a 500GB SSD or maybe a pair and put the rest of the stuff on a NAS somewhere. I haven't investigated, but I wonder how fast this will be in RAID 0 configuration where you have a pair of these, can you saturate a pair of 6Gbps SATA channels, I wonder 🙂 The ASUS P8Z77-V has a pair of SATA 6GBps controllers that can boot in RAID 0 so theoretically, you can get amazing bandwidth.
Samsung 840 coming
The just announced Samsung 840 uses the new 21nm process vs the 27nm of the 830 using Toggle 2.0 NAND (wow the names in this business are incrdible!). and is about 10% faster than the current 830. The sweet spot price remains at 256GB. Amazingly these chips even include a 512MB cache.

Samsung 830
Tom's Hardware has a good summary:

• For $230 or so, you can get the Samsung 830 256GB SSD. We actually have two of these to be used for notebooks already. They read/write at an amazing 520-560MBps. Getting a pair of these gives you 512GB for$460, so very expensive compared with disks, but on the other hand less noisy and definitely faster. Amazon Newegg has the standalone version for $220 right now, but the desktop version for some reason is cheaper at$200.
• There is a smaller interface called the mSATA that many motherboards have, the Mushkin Atlas 240GB has the same performance as an SATA SSD but in a tiny form factor at $350, make some sense if you are building a smaller system. • For$400, the Crucial m4 512GB is an amazing amount of storage, the main tradeoff is that it's write speeds are half the reads, so less performance than the Samsung

To give you an idea of the difference, here is Tom's overall chart where Samsung 830 scores 201 average data rate vs Crucial m4 at 167. I don't know if you can RAID 0 these as boot drives for Windows, but a pair of these in RAID 0 would be amazing.

Anandtech shows a very similar analysis showing that architecturally, the Samsung is pretty good right now