Computer Advice

[sanddrag]

I'm looking to redo a few computers for myself this summer. I can either build or buy. Not sure which is more economical. I'm looking for three systems, a desktop, laptop, and home-theater PC. Below, I'll list what I need them to do. I'm interested in hearing your hardware or system recommendations. Also, the Lenovo Outlet has some pretty good looking deals right now. I was wondering if any might be suitable.

Desktop
I'm thinking this should probably be a mid-tower form factor. The desktop needs to run Inventor and Solidworks well (large models such as FRC robots) without lag, and needs to output to two monitors. I'll sometimes watch TV on one monitor while working on the other. Occasionally I might want to convert some recorded video and burn it to DVD without it taking an eternity. Rarely I might edit some video in Windows Movie Maker or something of the sort. I want it to be lightning fast for any normal mundane tasks such as web browsing or MS Office, which most computers nowadays are anyway. I often web browse with up to 20 tabs open in Firefox. I'll probably re-use my WD Caviar Black 1TB hard drive that is about 18 months old. I might stick a TV tuner in this system and record a bit, or I might record to this system over the network from the HTPC tuner. I don't think a Windows 7 PC can yet act as an HTPC extender right? So I might stick in a second drive for recording. Although I could just have a network share on the HTPC. One oddity is that I'd prefer this machine to have an internal floppy drive. (I still use the sneakernet to get files to my CNC which runs DOS).

Laptop
The laptop needs to run SolidWorks and Inventor reasonably well, to the point where it doesn't have to be blazing fast, but still usable for models such as an FRC robot. I'm not super concerned about battery life, but of course longer would be better. I'd prefer something without a 10-key. I really like my current Acer laptop. Built in bluetooth would be good. I need at a minimum a 250 gig drive. 7200 RPM would be nice, but it wouldn't kill me if it was the standard 5400 RPM.

HTPC
I want to use a Ceton InfiniTV 4 cablecard tuner. So, it needs to record up to 4 digital HD channels at once, and potentially offer its tuner over the network. Probably a single Terabyte drive would be fine for my TV watching habits. Not sure that I need Blu-Ray yet. Output would be over HDMI to a 42" LCD. This machine would also be used for web browsing and e-mail. This machine needs to be as small and quiet as possible and have as little power consumption as possible.

All systems will be running Windows 7 64-bit.

I'd like to keep the cost under $700 each. I'd be happier if the laptop was closer to $500. Not sure if a $500 laptop will do what I want with CAD.
I'd like them all to last me at least the next 3, preferably more, years before doing any big upgrades or replacement.

My current desktop is a P4/2.4/512/533 (going on 8 years!) with 3 gigs of DDR RAM, a tuner, Windows 7 32-bit, and an Nvidea Geforce 6200 AGP 8X.
The laptop is an Acer Aspire 4720Z with a Pentium T2330 with 2 gigs of RAM and Vista 32-bit.
Solidworks is far too slow on both of these machines.
No HTPC yet.
Anyhow, time to upgrade.

So, any recommendations?