Don't think i've ever seen a normal person that got 300rwhp with them, in fact, i've seen nothing even close. When i say "normal" i mean a guy that's not building a car to fit into a race class, and is willing to spend what it takes.
300rwhp is going to cost you way more than they are worth in head work.
Use them for what they are, and when you need more power sell them them and buy something better.
They are a mid/low 13 head.