[Solved] First time build - cheap i5 possible?

Good news is, its possible and under $800. Depending on the options for upgrades will effect how much under you can come though.

From ZZF, must buy at least parts for these prices. And almost all ZZF products, including cases have free shipping:
$183 amir i5 750 http://www.zipzoomfly.com/jsp/Prod [...] e=10011084
$23 amir DVD burner http://www.zipzoomfly.com/jsp/Prod [...] e=10010714
$44 http://www.zipzoomfly.com/jsp/Prod [...] ode=141815
You can pick any case you like, just adjust your budget accordingly. Try to look for free shipping as cases usually pop you for $20 alone.
Neweggs cases w/ free shipping: http://www.newegg.com/Product/Prod [...] 20Shipping

From Newegg: All these items here have free shipping.
$30 amir 500w OCZ StealthXstream PSU (ON SALE TODAY ONLY) We'll adjust and find something else if you can't grab this. http://www.newegg.com/Product/Prod [...] 6817341012
$185 Gigabyte UD2 mobo and GSkill DDR3 4gb 1600 Cas7 ram http://www.newegg.com/Product/Comb [...] mbo.264221
Mobo: http://www.newegg.com/Product/Prod [...] 6813128405
Ram: http://www.newegg.com/Product/Prod [...] 6820231279
This mobo isn't CF ready, so if you want that as an option, expect to spend another $50 or so.

$155 500gb Spinpoint F3 HDD and Windows OS http://www.newegg.com/Product/Comb [...] 22-152-181
HDD: http://www.newegg.com/Product/Prod [...] 6822152181
OS: http://www.newegg.com/Product/Prod [...] 6832116677
This can change as Windows 7 will be out Thursday

So before the GPU, you have ZZF $280-$30mir + Newegg $390-$20mir = $620

As for the GPU, at 1440x900, you can go lower end and upgrade later, or spend a little more now. Depending on how soon you can get a monitor upgrade really should determine how much to put in the GPU. I'll go the lowest and highest, you can pick where you want. What would be nice is if Toms hits us with an updated Best GPU article.

Great for now, but won't do much on a 1920x1080:
$40 amir 4670 1gb DDR3 http://www.zipzoomfly.com/jsp/Prod [...] t=celebros
This card is a steal at $40 for 1gb DDR3.

If you want to spend all the way up to the $180 left (depending on case and mobo choices) and have something that will run a 1920x1080, the 5770 is an option:
http://www.newegg.com/Product/Prod [...] 0HD%205770
There's some good PSU combos with these too so you can get a beefier PSU for the same cost.

If you're not overclocking the CPU, then the case will be fine. It offers much better cooling than an HP or dell ever would. You also have 2 side vents where you should be able to stick an 80mm fan if you really needed. My system is an OC E5200 and only has 1 side vent with a fan and nothing in the back and my 4850 dumps the heat into the case, not out the back.

As for the PSU, the one I linked is upto $40, so we'll find you a different one when you're ready to buy. Depending on the mobo you choose, a 550w will be enough for most any single GPU that would fit your budget, and 650w w/ 4pcie connectors if you want a CF or SLI option. That also means more on the mobo as stated above.

Windows 7 comes out tomorrow, if you can avoid buying tonight, you won't have to wait.

Depending on what HEAVY multitasking is, 4 gb should be enough. The 6gb kits are for triple channel mobos, but the P55 boards are only dual. So you could go 8gbs, but I'd wait and add the second kit later if you find you are using all the first 4 gbs.

Something else to consider depending on what the multitasking is, if you do take a lower GPU option and single pcie 2.0 x16 mobo, you could get the i7 860 and keep the rig under $800 still. Depends on what your goals are. Is it cheapest quad possible, or most performance for $800?

The nice thing about the 5770 I have have there is its a dual slot rear exhaust cooling solution. So the majority of the heat produced will be vented out the back of the case, and not into it. Cases are a very personal choice. I recommend getting something you really like the look of.

One note about that mobo and 2x GPUs I just noticed, being a micro ATX board and using 2x GPUs, you'll end up covering the pciex4 and pci slot from the case of each GPU. If you have no need for the extra slots, then its not an issue, but it does limit the option of adding any other type of cards. But they usually go unused anyway because the mobo has great sound and the network card built in.