Like you, I don't make large amounts of dough at one time, so my simple KitchenAid mixer meets my needs. However, if I were considering a new KitchenAid, I would seriously look at one of the Professional 600 series models--like the one Pftaylor has with the new dough hook that seems to be much better than the old-style hook. Also, you never know when your needs might change in which case I would rather have a higher powered unit that can better handle larger amounts of pizza dough and be less likely to break down or result in stripped gears (which apparently is quite common). From what I can tell from member feedback, it looks like the new dough hook may work with small amounts of dough because of the large number of contact points of the new dough hook. However, I would want confirmation on that point before going out and spending more money for the bigger and better unit. In the long run, the difference in price will be insignificant, but it is nonetheless still important not to have a unit that doesn't meet your requirements.
BTW, I have seen several of the 600 Series KitchenAids on eBay at prices that seem quite reasonable compared with many other sources I checked. Some of the machines are refurbished but many are new.