All of the above mentioned things are great ways to improve the speed that your phone interacts with you. However, I'm afraid that in the case of the 8330 themes are a speed killer hands down to the phone. I've used so many beautiful and aesthetically pleasing themes on my phone that take advantage of OS4.5 and whatnot, but the fact is, I still lose the speed that I had with my Verizon theme that came with the phone.
Try to keep a simple theme on the phone, also hiding unused icons on the main page and removing unused applications from the Advanced Options menu will help drastically.
"He that hath no sword, let him sell his garment and buy one."
Jesus, Luke 22:36
"The deadliest weapon in the world is a Marine and his rifle."
Gen. John Pershing, U.S. Army