Your ideal (realistic) build

Sub. 4000$... Are you for reals? I don't think that build ^ costs that much. Umm question... What are you using it for? Like gaming, video/photo editing (if so which programs), and yeah...

An ideal Adobe Suite CS5 build for 2011 would be...

Any CPU above the i5 2400S performance from Sandy Bridge
Two SSD's (Like two S599's http://www.guru3d.com/article/adata-s599-100gb-ssd-revi...) in RAID.
2 HDDs for backup/storage (Samsung F3 1TB)
8GB of Mushkin Ram (all preference) dual channel
Any mobo really
GTS 450/460 (utilize Mercury engine in CS5)
CD/DVD drive
Screen

All I can think of.

^ Mmm, no I'm just asking you to just imagine it. It's amazing how differently people spend their money.

I intend to use my computer as a portable light duty Photoshop, Illustrator, Painter and Sketch Pad. It'll be like a netbook with higher performance, a decent display and bigger screen.

If my IPS panel has RGB LEDs it might cost $2000, I dunno...

I set $4000 because I don't want people holding back.

Well, the simple fact is that the apps and games I run perform well enough on a 740BE (unlocked to X4)+HD5770 or an i5/650+GTX460 that I can't justify an upgrade for performance reasons. When I do upgrade, it will be for educational / current experience purposes, probably not until late Spring or early summer, and mostly likely focused on lower power consumption rather than increased performance. I doubt I'll spend $1000 on it, and that much only because it will include a 128GB SSD.
The remaining $3000 would buy a nice little shed for the back yard, and allow me to insulate and electrify it to use as a workshop / hobby room :-).

^ Haha with the 3000$ I'm getting myself a Canon 50D and saving the rest for a car.

I agree.
Spending 4000$ or even 3000$ for a PC would be overkill in most situations,
unless you got some really heavy computing tasks needing to be done.
In fact, I'd say that even above 2000$ you would be slammed pretty hard by the law of deminishing returns  

I never told you to spend all of it  .

I mean if I had "unlimited" funds, I would build several computers.

I'd have a gaming rig with an i7-900 series CPU and Tri-SLI GTX 580s (or something like that) with 6GB RAM and a SSD, etc etc.

I do use MATLAB a lot for my engineering classes, so I would like a server to compute all of that (you know, dual Xeons, 24 GB RAM) and to use for all of my movies and such for mobile/home theater use.

I would top that off with a MacBook Air for productivity on the go. I really like Mac OS X on my mobile devices, and love the size and weight (or lack thereof) of the Air. I really only use Office as a student, but ideally anything else I could run on my server.

If I had $4000?

Probably dual X5680's

Throw in a high end Quadro card and more RAM than I could ever probably use. And while I'm at it, maybe a couple of new SSDs.