If you do plan to compete, I can make a few suggestions. First and foremost, take a good look at the rulebook. SCCA is very firm in allowing given mods relative to the car's (competition) class. Wheels and tires and #1 on the list and will bump you into a situation where you won't be competitive in an instant. This is, because, the tires will make or break the car is SOLOII. Once you pick a class, get the right tire. As a rule of thumb, in solo events, the driver is 70%, the tire is 20%, and the car makes for the rest. Again, the choice of tire will hinge on the class. At one time, we ran an A2 GTI in DSP with all of ~100HP and we've finished as high as 4th overall against a very competitive field that included an ex-F1 car. It's the one behind the wheel that determines success; it's not the mods.
As you seem to be fairly new to this, which is fine, do yourself a favor and look into attending an SCCA-sponsored school. The instruction is offered at a nominal fee, and the experience is invaluable. I suspect that you've never driven competitively before. The constraints and driving techniques differ greatly from what one does on the street.
As for Time Attack, don't even dream about attending before running SOLOII for a few years. Once you get that experience, attend a few road racing schools. While there's more similarity between road racing and auto-x, relative to auto-x and the street, it also necessitates a specific skill set that doesn't really come naturally. If you do decide to compete, you'll meet great folks at every level who'll steer you the right way. I'm just hoping you'll look into a school. Best of luck. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
You may want too look into the weight of the wheel/tire before making your selection, along with the rulebook I mentioned above. There's literally nothing that will kill the car's dynamics quicker than an addition in rotational mass. The farther that mass sits, relative to the outer circumference, the more effect it has. As such, tires and #1, wheels are #2, and brake rotors are third in line in terms of significance. The reduction in rotational mass can be dyno'd as well. Ask me how I know.