I'm working on improving a pasta dish of mine. The main ingredients are onions, mushrooms, garlic, olive oil, butter, balsamic vinegar, and herbs like basil and sage. Oh yeah, and pasta! I usually put heavy cream in it and let it thicken to a nice cream sauce but I'd like it to have a little more flavor and be slightly more creamy. Cheese should do the trick... but which kinds would be best?

Also, if anyone knows how to add the cheese so the sauce is nice and smooth and creamy and not clumpy and seperating (from the oil and heavy cream mixing) please share!