Sounds like you're a high flight/spin player which is what I am as well.
Changing to the 510TP DF will help since that's one of the lowest spin heads ever. But be careful with shaft selection, and make sure you get a low spin model like a tipped Accra 70, or the fuji 757. The 510 is like your 300's, the best product TM has put out. I was talking to a Titleist rep and he said that hte 510 is the hardest club to pry out of anyone's bag, professional or amateur. I bought a tour R7, and it's just gathering dust because it just doesn't feel as solid as my 510.
Your current shaft is suited well to your high launch style, but may be taking away from your swing speed. If you're still hitting the ball too high, it may be a swing issue, possibly club ahead of hands at impact, maybe time to see your PGA pro.