I've tried several different oils in the K20. Just use any 5w30 if you drive conservatively. For regular VTECing, I do recommend you use at least an OTC synthetic (Mobil 1, Pennzoil Platinum, etc). Pennzoil Platinum can be had for a very attractive price during promotional sales.
I use 195W-385 weight oil for peace of mind. I have a stage 9 aftermarket kit, which raised my redline to 22,000rpms. I also enjoy redlining as soon as I start my car every morning. Even if I don't plan on going anywhere.