Tax returns and off camera lighting

[Rocco]

With tax season comes camera gear. This year it will come in the form of a new laptop with workstation discrete graphics and an IPS panel display, as well as PW TT5's, a TT1 with AC3 controller, two more flashes, and light modifiers/stands. (If you didn't read the thread, my new year's resolution was to become a proficient strobist.)

I have a question about the flashes for you strobists on here (Sean, you listening?!). I have a 430ex II right now. The two flashes I have on the handy little spreadsheet I made (that already has all my tax returns spent by my count) are 580ex II's as well as the CP-E4 battery packs. Other than the loss of the battery packs and weather sealing, is there anything else that I would lose by getting two more 430's instead? I've read a little about the guide numbers, but it means almost nothing to me. How much of a power difference are we really talking here?

As far as light modifiers go, I'm looking primarily at Wescott products with Manfroto lightstands/umbrella swivels.
*Wescott 60" Optical White Satin umbrella with black cover
*Wescott Compact 43" White Satin umbrella with black cover
*Wescott Apollo Orb Speedlight Kit
*Rogue Flash Bender - Large

Anything you would suggest I get instead as far as modifiers go? Or is this a pretty sound set-up for a budding strobist?

And before someone mentions it, I'm sticking with Canon here so I can retain eTTL functionality.. as it does have it's uses.

Thanks guys!

-Rocco