EP3/DC5 guy here.
Driving experience aside, if you want to be fairly competitive in local sanctioned autoxing, you can do ok. Anything else , you're in the wrong car and it's been proven time and time again. Lots of suspension design weaknesses. To make the DC5 handle really well, which it can, you'll get bumped into even faster groups and will not be competetive. But you will have lots of fun.
Will this be a dd and part time tracker? What's your budget? I wouldn't go near the Maxxis tire level without a season or two under your belt. I would consider getting your understeer to a controllable level and a few other things or you'll be very frustrated with the handling.
Did you just buy the BC coilovers? I hope not as there are better options for a similar cost but they are pretty decent. Someone mentioned doubling the size of the rear springs in relation to the fronts and that's pretty much the case but not essential with a 10k front. 12k/680 lb. rears won't cut it eventually, though. The motion ratio in the rear requires around double the rate to compensate. I'm pretty sure you can up the rear springs a little without having to re-calibrate but I'm not sure. With the 10k fronts (560 lbs.) and stock weight you're just at the point where you can remove the front bar and really improve the balance. I wouldn't waste your time upping the rear to 22mm as the 2005-2006 S bar is 21mm and you'll barely notice the difference. If you do get a bar, start with the Progress 24mm. It's adjustable, has a reinforcing plate to improve the connecting point strength, and comes with end links, shipped for $260.00 from K Series. But you could hold off for the meantime with a new rear bar and play with tire psi and alignment.
Down the road, if you want to get serious, the rear suspension will need big boy springs as there are several weaknesses that need to be minimized.
Your oem bushings, front and rear, have been toast for a long time. Go with harder rubber or Energy Suspension or even poly offset or solid offset bushings, depending on how serious you are. I mean if you're in there, you might as well do it right so you don't have to go back any time soon. Also consider Type R lcas as they widen the track, weigh 6 lbs. less, and give you some caster. Big difference. They also still might have decent harder rubber bushings in them. Caster is a HUGE need for the DC5/EP3 due to the McPherson-deminishing-camber problem. More on caster if you want to know.
Definitely get front camber bolts. I think one per side will net up to -1.5 or thereabouts. -1.5 would be ok to start but it isn't the same car as when around -2.5 to -3 so consider 2 per side. Or caster/camber plates. The rear camber is generally set at about 1/2 the rate of the fronts, depending.
Since you need tires, you might as well go with Extreme Summers, although some might feel you should go with less adhesive tires to start with. The RSX has pretty big wheel wells but you might start out with 225s or 245s, although you can reverse stagger with 275 fronts/245 rears. Your K20 and lsd can handle some nice tread...
Btw, you are already at 205 whp., you would probably be faster at this time without the 230hp. The DC5 needs more control before hp.
Those are some of the basics for a starter at stock weight. My EP's weight is -430 lbs. at around 2350 lbs. and dropping at least another 100 soon with a final goal of 2175. That's Gen 5/6 territory and it's a completely different car (close, but it's still not a gen 5/6) without the weight and is still my dd. It just depends where you want to take it.
That's it for now. As with any car, there are lots and lots more tricks.
edit; forgot, don't lower suspension more than 3/4 -1" or your handling will definitely suffer. There are ways around this but at a more advanced level.