The 430EX will give you just about everything that you get from the 580 series flashes except that the 430EX cannot be used as a Master in a master/slave setup. However, in order to use the 580 as a master, you would need to purchase another 580, a 430EX or a used 550EX or 420EX. Since you would need to purchase another flash anyway, why not wait until you identify the need for a master/slave setup. That need may never come along.
Oh yes, the 580EX is a bit more powerful than the 430EX but, the 430EX would probably give you all the power you need.
I would recommend a reflector diffuser for your 430EX. Try a Joe Demb Flash Diffuser Pro (DFD Pro). This unit is priced reasonably and does a lot to modify your hotshoe mounted flash. I love my DFD Pro and use it either while my flash ismounted on the hotshoe or when I am shooting with an off camera flash bracket.
I ALWAYS BOUNCE MY FLASH whenever possible. There is a lot of flash information on this site.
http://www.dembflashproducts.com/diffuser/models/
This reflector/diffuser unit may be all that you need to achieve the lighting quality which pleases you. I would advise trying it first and then deciding if you want to go further. Further purchases would include a Canon (or Third party eBay brand) off-camera flash sync cord and a flash bracket which will hold the flash unit directly above your lens in both the horizontal (landscape and vertical (portrait) camera positions. I have no problems buying Chinese knock-off merchandise when the cost differential is great but, I use a Canon OEM off camera cord.
If you decide you want to use an off-camera flash setup; I would chose a "camera-flip" bracket over a "flash-flip" model because when you are bouncing your flash and switch from horizontal to vertical position with a flash-flip unit, the flash is pointed in the wrong direction and you need to re-orient it. This is not difficult but, takes extra time and is just one more thing to forget in the heat of shooting. I have attached images of a flash-flip and a camera-flip bracket in the vertical position to show you what I mean. By the way, in the interest of simplicity; I have not included the required off-camera sync cord in my illustrations.
I use a Chinese knock-off of a camera-flip Stroboflash flash bracket and it has functioned fine at a fraction of the Stroboflash price.