I run 48x16 and it's just about perfect for now. I top out at around 23mph or so on the flats, too. With a lighter wheelset, I plan to go to 50x16. If you want to go to a higher gear, I suggest you lose some rotating weight (rims and/or tires) to make up for the loss of acceleration. That's basically the same I did. My Kenda Kalientes are nearly a full pound lighter than the crappy tires that came on my bike. Once I swapped to the lighter tires, I found my 46x16 gearing was way too easy to pedal. I went to a 48T chainring, and it has the same acceleration and climbing feel as it did with lower gearing and heavier tires. The only difference is, I'm 1-2mph faster at all times, and I have a higher top speed.

BTW, there's nothing wrong with mashing if that's what you're into. I can spin all day on my geared bike and wear out my knees and quads, but I have a better ride standing and mashing in a tall gear. After a 50mi ride with a 78.8GI set-up, my legs and body felt fresher than a typical 25-30mi ride with gears.