Poll: Appropriate GPH for this waterfall?

[^iMp^]

I've found a few calculators online, but they don't seem quite right. For reference, the current flow rate is around 80-100 GPH. I'm using a weaker pump because a) I want to keep the wattage down, and b) my wife can't stand any "trickling" noise.

I realize that some seepage will occur around the waterfall. This is fine, as I have a substrate drainage system in place.

I'm guessing that I can go for 300gph without much trouble (except maybe from my wife). Note that the waterfall is supplied by ~1/3" tube (at least at bottlenecks in the line), which may limit flow (not an expert in fluid dynamics or plumbing, for sure).

I know this is a difficult question, but I'd still like to know your opinions. I'll use the average suggested GPH if I get enough responses.

Thank you!

^iMp^

edit: Ugh! I used you're instead of your...I need to go shoot my foot off or something.

[^iMp^]

I'm currently looking at:

http://www.marinedepot.com/a_ph_dolphin.asp?

Do any of you have experience with these pumps? Are they relatively silent and durable? I'm looking at the DP-270 and DP-385 in particular.

^iMp^