My setup is nearly fully pimped out, I am also in the same boat but I got all my upgrades considering moving it onto a larger setup. The thing is I quite like the size of the phantom and though I have 6 tiger motors I dont see the need for anything larger then a quad. I have no interest in flying cameras larger then a gopro and gimbal and my setup has shown this can be flown quite well on a quad. 450 size will allow larger props but then its more of a pain to transport it, the main thing that makes me consider those is the battery size limitation and I want to keep it mostly inside the shell. If I went for external batteries in a phantom I figure I may as well go for a TBS, 450 frame or maybe something waterproof in that size.
My next and last mod to the phantom will be the last parts I need for the next build, that is getting some 30a ESC's. I want to first try this in the phantom along with a 4S battery and going by the specs on my tiger motors these will give more lift then I will ever need out of a quad.
Using that chart a 4S with APC 10x3.8 props (very similar to flying GWS 9050 triblades on phantom) for a larger build I would go for larger dual bladed props but phantom cant do 10 inches but the GWS tris I find are fine as is. At 4s thrust @50% throttle would be 540g per motor and 100% 1280g per motor, if anything this may be too much thrust and at 1.2-1.3kg it could cause motors to shutdown needing well under 50% throttle for hover.
Compare that to 3S where it fly's quite well 50% 370g and 100% 900g thrust so 50% is 1480g thrust on a quad with these motors and apc 10x3.8 and quite likely very similar to the GWS 9050. This is not much more then my current setup weighs and in manual mode I am at just below 50% throttle with these props in a hover so it seems quite close to those figures.
Going by the 4s specs and being able to easily lift more weight I should be able to use much larger batteries around 4500-5500mah and still get plenty of lift. May be pushing the phantom frame itself a bit but also the GWS 9050 props are best for 4s and kv750-800 motors. So in that case I kind of wish I went with kv800 instead of kv900 motors but still worth trying on my current ones. If no good I will simply stick with a larger 3s battery.
http://www.multiwiicopter.com/products/sku-27
I am considering getting a phantom v2 shell and putting my stuff into there if its around the same price as the current phantom shell being $49 at Multiwii then I will gladly give this a go along with the ESC's and I will also make a custom board getting rid of the DJI mainboard I really dont need anymore. If it doesnt really work then I will simply look at the larger frame options but first want to see what I can get out of the smaller 330 frame that is big enough for lifting a gopro and gimbal.
I am fine with NAZA v1 and PMUv2, I dont think I need WKM or A2 I rarely fly in GPS mode and have no interest in automated flight.