your best next upgrade would be a higher tow rope attachment. An inexpensive tower, such as from here: www.diywake.com
or possibly even a used on for less on ebay or craigslist.
This won't make a better wake but will give you a better pull and more air time from your existing wake. Before you spend a lot on fat sacs and pumps, load your boat down with a big crew and see how it responds to the weight.