Questions on hardware setup

First, let me say that this is my first of hopefully many posts on the Cakewalk forum. Greeting, best wishes, and happy music-making to all.

I am setting up a home studio. I have already purchased everything I need (I think), and much of it is being shipped to me now. I am not an experienced audio technician, but I have tried to read up enough about this stuff on the net that hopefully I have not made any major purchase mistakes. At least I know that I got everything at very good prices through some major web-surfing and e-bay-hanging-out.

OK, here is what I either already own or is on its way:

- dedicated desktop - windows 64-bit, dual 2.5 ghz processors, 4gb ram, two open firewire ports and 2 or 3 open PCI slots, 640 gb internal hard drive, standard integrated audio and video cards, standard ethernet card, ATT Uverse connection at speed of "up to 10 Mbps."
- dedicated Seagate 1.5 tb external firewire hard drive
- M-Audio Oxygen-61 MIDI Controller
- Mexican-made Fender Stratocaster and cheap line 6 amp
- M-Audio cheapo ($99) pair of powered monitors
- Grado Prestige SR-125 headphones
- Rode NT-1A voice mike with stand and cable
- Cakewalk Sonar Power Studio 660 with SPS-66 audio interface and (I think) Sonar Studio 6.2.2 software (haven't laid eyes on it yet and it's hard to figure out exactly what the software that comes with Power Studio 660 is
- Propellerhead Reason 4.0

- Does anybody know whether the SPS-66 has two firewire out ports? If it does, then the Seagate drive hooks to the SPS-66. Otherwise it hooks to the desktop.
- Either the monitors or the headphones also hooked to the SPS-66
- SPS-66 hooked up to an open firewire port on the desktop
- I can hook up the mike, guitar, & MIDI controller straight to the SPS-66 simultaneously, right? And I don't need an amp at all, right?

Installation: Propellerhead reason 1st, then Sonar, then I use something called Rewire to slave the Reason to the Sonar, then I hook up the hardware and configure it to sonar.

Questions:

Am I missing anything vital?
Doing anything wrong?
Is there a better way of doing anything that you would recommend?
Do I need to disable the internal sound card?
If I have to hook up the drive to the desktop, does that create any latency problems?
Finally, does anybody happen to know whether Power Studio owners are eligible for software upgrades? I would sure like to lay hands on Producer 8.3 - will I have to pay full price for it?

Any other comments are very welcome.

Once again, greetings to everyone.