Thanks for the responses. I will likely never go beyond five gallons -- in fact, I'm considering doing smaller batches since I'm in the phase of getting to know the ingredients and techniques, so I don't really want five gallons or more of something I'm not fond of.
What I've learned from you (and others) so far is that, for most Belgian ale recipes, it doesn't seem that you have to worry too much about ease of conversion since they use mostly modified pilsner grain. Also, again from Denny Conn, that running the grains thru the mill a couple of times ensures a higher mash efficiency without a great concern for a stuck sparge. I will more than likely at least start with a single infusion technique until I get proficient, then maybe do a more complex mash schedule.
What I'm looking for to fill in the blanks is whether mash pH or other water factors should be a big concern or even be monitored as I start on the all grain path as well as anything else that I could be blindsided by. I feel quite comfortable with my fermentation, yeast starter cultures and sanitation techniques and have software for creating recipes so I have a sense of OG, bitterness ratio, etc. I've had great success with some high OG Belgians, such as Tripels and Strong Goldens, so I guess I'm really looking for advise on how going to an all grain approach is going to introduce additional factors. I'm hopeful from the many who say that the quality will go up. My goal is to make great tasting Belgians (and other types, but mostly Belgians) and I really don't care much about competition -- it's about pleasing my taste, so I don't worry much about conforming to style guidelines. I like the traditional Belgian approach of making what you like and not worrying about how to categorize the beer.
Thanks for your help!