Tony,
This is a subject that you will find a thousand different opinions on, so this is just mine, which is gathered from others who I believe to have experience in the field far greater than me. Basically you get what you pay for. If the deal seems too good to be true it probably is, however it isn't so much the case for PC hardware. If you are willing to do some investigating (and if you're into simming then you are use to this!) you can get yourself a system that will satisfy for the next 5 years or so. A very good piece of advice I read from an experienced hardware simmer on Avsim stated "if you can't get a 10 fold increase in performance from an upgrade it's not worth the extra expense". Many enthusiasts talk about a CPU upgrade that will cost them an extra $500 but give an extra 5 FPS increase. Up to the individual whether that's worth the cost (I'd say not).
Now, with the cost of hardware today being so competitive and sometimes reasonably priced, upgraders are in an ideal position. BUT, you have to know what you're looking for! For example, the system I spec'd, was built for $1600 AUD. Not a bank-breaking amount by anyones language, and it has the capacity to upgrade in the next 12 months to the newest processors (at a more reasonable cost).
To get to your Bare-bones system specs, definitely go for the second deal utilizing the Intel Q6600 and the 800Mhz RAM. I use to be an AMD fan but these days Intel has it over AMD when it comes to processors (that of course may change in future and ultimately is only my, and the general, opinion). Go for the motherboard that will accommodate the fastest processor, plus the ability to have extra PCIE cards. You need to map out exactly what your sim will require such as the number of monitors which will determine the number of video outlet etc.
So in a nutshell: Get a good quality motherboard such as Gigabyte, Asus, MSI etc. preferably of the P35 variety (best value currently), with 2 x PCIe slots (doesn't matter whether both slots run at 16x as the second video simply hangs off the first and SLI doesn't offer a lot with FS. The faster RAM the better, so get the 800Mhz. 2Gb RAM should be a minimum for simming and will assist FS greatly. Get an aftermarket CPU heatsink and fan if you intend to overclock, which is a cinch today. Here's a
LINK to overclocking the Q6600 which I used successfully. Get a name brand power supply of at least 600W to accommodate the components and overclocking.
The second deal you mentioned fits into my recommended category so you won't be dissapointed. As for the graphics card, FS is more dependent on CPU than GPU so video memory isn't as important an issue, however if you intend running multiple monitors, memory is an issue, so again it depends on your setup. However, the 8800GT is far and above the better deal these days both price-wise and power-wise, so don't go for the 8500 as your main video card, instead use it as your secondary card. As for hard-drives, many advocate RAID but I have opted for a single fast drive as my system is dedicated to simming and will do no other task. Again it's up to your requirements as to what you decide on.
As for operating system, if I wasn't looking to use 4Gb of RAM I would have stayed with WinXP as it is rock solid and there's no issue with driver/software incompatablites, so for you looking at 2Gb of RAM get WinXP Home or Pro (doesn't really matter sim-wise). Vista offers support for DirectX-10 but you can probably do without that for the moment. Having said that I have had no issue with Vista64 (SP1) and all its upgrades so far, and it runs FSX beautifully.
The computer store I deal with will build my personal system for $100AUD if I wanted (which I didn't cause it's fun!!) so getting the pro's to build it for you isn't a huge expense. I would get the second system pre-built and configured ready to load all your favourite FS system and addons and watch it fly when you load it up!!! You won't be dissapointed.
Regards,
Ken.