Just my 2 cents, P6 vs. P226, the P6 is slightly smaller, thinner through the butt, and easier to conceal, also has a slightly more rounded butt. Magazines are expensive but if you persevere you can find used surplus mags occasionally for around $20 each, I bought four when I had the chance. DO NOT buy the ProMags stick with the SIG Sauer product.
Differences between the P6 and commercial P225? P6 hammer has a strange little notch in it, it's a dropped weapon indicator. P6 has a MUCH stronger double action pull-have a set of Wolfe springs to install when I get the yard whipped into shape. P6 sights are plain black, no dots but commercial take off sights are cheap-have a set to put on, SIG and "brand-X" tritium sights are also available. SIG Sauer sights are numbered, higher numbers aim higher, that means you can raise of lower POA by changing either front or rear sight to a higher or lower number. SIG SAuer sights are pretty good, the rear sight is rebated so the notch is in shadow and gives a pretty good picture.
It shoots pretty well SA, not quite as nice as my buddy's CZ75 compact (which I shoot better than he does, BTW, but that's 'cuz I just shoot more).
So far I have the pistol with two mags for $350, $80 for four more mags, $25 for springs and $15 for sights. I'd like to put a set of wood grips on mine, but the cost is prohibitive, can't make myself invest $80-150 for grips for a $300 pistol. The factory plastic stocks are nice and thin (I have smaller hands) but aesthetically unappealing, and Pachmayr is again making wrap around rubber grips. It's much less pretty than a commercial P225 but it does the same job for much less money, too.