I've seen machines do some weird things with bad RAM or a bad CMOS battery. I suspect your real problem may be one of those. An i7 is nothing to sneeze at, so I really think what you need to do is address the noise you're currently dealing with.
I do agree however. New Dell machines have very good thermal control of fans and noise is far lower than previous desktop systems. Since PWM has been available for Desktop machines, Dells have been doing very well with the feature.
If your current i7 machine hasn't lasted you 5 years (and the first i7s are only about 5 years old now), a new one wont really last you 5 years without taking care of it. That starts at turning the machine off every night. Running it constantly doesn't cause a rapid decrease in lifespan, but it allows the hard drive to burn hours, and dust to get into the system, when it could otherwise be off, avoiding both of those problems.
I think you could upgrade your current machine to an SSD, new fans, and better cooling, as well as sorting out the booting issue for far cheaper than a new system. If your current machine is more power than you need (and it likely is), there's no point in upgrading to even more power than you'll need, even thinking ahead. I work in a computer shop, and while it's your decision in the end, you're hardly running "outdated" hardware. I do see customers get upgrade fever like this fairly often, but just like I would say to them, if this machine still has more than enough power to do what you need it to do, it's not yet time for an upgrade. If some part fails that is cost prohibitive (meaning it's cheaper to upgrade than repair), then fine. Nine times out of ten, the reason it becomes cost prohibitive is because of the labor cost, not the parts needed.
I would say rethinking the case fans is your #1 priority, then getting a new CPU cooler, then upgrading RAM, then hard drives.
Literally 1-2 case fans is more than enough, upper and rear exhaust only. No intake fans. None.
1366 heatsinks are easy to find, and you could probably toss in an HR-02 Macho, and never have to think about it again.
You haven't mentioned how much RAM you have. Triple Channel is a PITA, and I hate dealing with it because of the kit prices, but as long as you're running Windows 7 Pro, you've got capabilities for all the RAM you're going to need out of a "basic" home machine.
That's just my $0.02 about this. Also, I own a 2011 MacBook Pro 15" and I can honestly say it's far from silent. I treat mine very well, but in a quiet room, it makes noise, and has a bit of vibration to it. Also, under intense graphics load, those fans kick in, and it's seriously loud for a laptop. None of my previous laptops have gotten anywhere near as noisy. An SSD would solve the vibration issue, but wouldn't change the fan noise.
|Dual Intel Xeon E5-2620-Xigmatek SD1283 DK-II|Asus Z9PA-D8-HR-05 IFX|WD 250gb Velociraptor SATA3|16gb DDR3-1600 ECC RDIMM|WD Blue 640GB SATA2 x2|Logitech K750|Logitech Wireless Mouse|nVidia GTX660ti 2GB|Antec HCG-750|NZXT Source 210 Elite|M-Audio ProFire 2626|Art TubeOpto8 with Smooth Plate Tube Swap|Avid Artist Mix x2|
A 9500GT with 1GB of RAM is the most pointless thing since NASCAR.