Wow... So after weeks of reading and figuring out if this is the car for me, I'm thinking about biting the bullet. Or rather I've bit the bullet, but only put down $500 so I can still walk away. So here is what I'm looking at:

2005 Shinka - 370xx miles
2 owners - 50 year old man and 34 year old woman
carfax - clean as a whistle
38 maintenance records found
all oil changes have been done at the dealer
extended warranty purchased - $75 transfer fee?
body is in great shape, interior is 9/10(a few stress cracks but no tears in the leather), and the engine bay was spotless
no engine replacement, yet...

So, I took it out, drove it around, looks and feels great. A little more cabin noise than i was expecting, but I heard that this is what I can expect from the stock tires.

Since I've only really had hand me downs and bought cars from family, buying a car from a private seller is foreign to me. They are asking 13k, which is an amazing price from what I've come to understand.

I'm curious what more I should be looking for and what more I need to do?
I just read about taking it for a compression test, should I go through a Mazda dealer for this? I live in San Antonio, TX, so it's hot as hell here, what oil should I be using?
I know about the premium gas thing and the fact I need to check the oil every time I fill up, is there something else I'm missing with normal upkeep?
It comes with the Bose system, and I was thinking about adding a bass tube or Inifinity bass link, good idea?

Ok, I think that is all. I really appreciate your help with this matter. I will get pics posted if the deal goes through! I would love to get tips sooner than Thursday, cause that is when we close.

For the most part unless you know a rotary shop in your area(or a member on this board with a compression tester) you must take it to the dealer for the test. The tester is rotary specific. While your getting your test done ask them to give the car a good inspection, it should not cost anything but even if they charge you an hours labor thats cheaper than buying a 13k car that possibly has some issues.

The oil thing is hard to say, everyone has their own opinion about that. I personally use 10w40 all year, it hits over 110 degrees here in the summer and the winters out here never get cold at all I can wear shorts in the winter. I suggest you do your own research on it though and figure out what you think is the best after lots of reading.

Thank you for the quick response! I have done a little more digging on the forums and found some answers that I needed. I also found the SARX club and hopefully can hook up with some of the members to get a better idea of what I'm in for here in TX. Thank you again!

^good idea.
Read through these as well
FAQ’s http://www.rx8club.com/showthread.php?t=959
New and Potential Owner’s, Start Here http://www.rx8club.com/showthread.php?t=202454
Congratulations, you got an 8 http://www.rx8club.com/showthread.php?t=202548
New Owner FAQ’s http://www.rx8club.com/showthread.php?t=163824&highlight=FAQ

Also, make sure you read the “stickies” in each sub-forum.
Good luck