Depends on the quality of the tyre you're using I reckon.
The cost of an 'ordinary' 255 width tyre might be the same as a really good 235 width tyre. The 255/40ZR17 Nexen N3000's that came with my mags when I bought them are nothing short of utter shite at the retail cost of $190 each, which is cheap for any brand's "top of the line" tyre. As a (bad) comparison, the 225/50ZR16 Falken Ziex 512 tyres I had on my old 16's absolutely shat on these Nexens from a rather great height in every way.
Even the 205/50R16 Vredestein Sportrac 2's I had on the front 16's had much better handling than the 225 Nexens I have now.
I suppose what I'm trying to say is instead of spending money on a new set of wheels with some normal tyres, get some decent tyres for the mags you have and you might end up better off.
I'm fairly sure that the wider the tyre you using on the front will give you heavier steering, which you may or may not want. I quite liked the difference in steering feel my car had when I went from a 205 to a 225.