Partial Mash Brewer-Making the jump to all grain

I've been brewing partial mash for almost two years now. Recently, my brother and I have combined all our equipment at his place and have been brewing a 5 gallon batch every Thursday and are having some pretty good results. We're starting to get the urge to try all grain, but want to know what we reasonably need to add to our setup to make that happen. I prefer to stick to 5 gallon batches and prefer to bottle since we're splitting, sharing and giving away each batch we brew. I'd also like the flexibility to brew fairly high gravity all grain beers up to 8 or 9 percent.

Current equipment includes:

1 - 6.5 gallon glass carboy
2 - 5 gallon glass carboy
1 - 5 gallon bottling bucket (plastic)
1 - Bayou Classic single burner propane stove
2 - 3 gallon stainless stock pot
2 - Auto siphons
1 - large diameter blowoff tube
3 - airlocks
1 - floating thermometer
1 - hydrometer
1 - thief
2 - bottle cappers
and of course other misc. equipment including funnels, strainers, brushes, sanitizer, hop bags, grain bags, tubing, carboy handles, utensiles, etc.

Equipment in the works:
1 - Digital Scale
1 - Wort Chiller (homemade out of copper tubing)
2 - Mash Tun (possibly converted 10-gallon igloo cooler)

Questions:
a.) I know I need a larger brew kettle for all grain and I prefer stainless. I would love to get a Blichman Boilermaker, but can't afford the pricetag right now. I see brew kettles ranging in volume from 5 gallons to 55 gallons. What size do I actually need to be able to brew 5 gallon all grain batches?

b.) I'm pretty industrius and think I have a source for a free keg from a friend that works at a local package store. Would it be a good idea to torch the top out of a keg and tap a valve and possibly a thermometer instead of buying a brew kettle?

c.) I know all mash requires bigger volumes of water and I have a hard enough time moving my 5 gallon carboys around when they are full. Is a pump setup necessary or is it still possible to sparge, transfer wort, etc. with siphons?

Thanks in advance for any advice and recommendations. I only found this forum about a month ago, but in that short time have gained more knowledge that I have in the previous two years of home brewing.

You definitely need a MLT, as you know. A keggle is nice to have if you can make one, otherwise you need a boil kettle of at least 40 quarts. Well, mine is 30 quarts, but it's not really adequate. You can do it if you have to, watching for boil overs like a hawk.

I don't have a pump, and I have a very simple set up. I have a boil kettle, a MLT, and a 5 gallon pot for heating my sparge water. You don't need a HLT if you're batch sparging, but if you're planning on fly sparging, they are nice to have.

One thing I don't see on your list is a good thermometer. You need an accurate thermometer for monitoring mash temps and making sure your strike water is the correct temperature. Otherwise, you seem to have most of what you need.

I guessing that your 2x3 gallon stock pots is all you have for mashing/boiling kettles. For big beers, you will need at least a 10 gallon pot, unless you plan on heating up your water/grains and transferring to a 10 gallon lauter tun. If so, you will be fine, but if not, get a bigger kettle. Get more blowoff tubes and more 5/6.5 gal. carboys too. Also get a good, sturdy spoon/spatula to stir all that grain/water.

For 5 gallon batches, the BK should be at least 8 gallons but 10 would be more comfortable and reduce the chance of boilovers.

Water management isn't that tough. You can heat your strike water, which shouldn't be more than 4 gallons in one shot, then start heating sparge water (also about 4 gallons) about half way through the mash. In other words, you don't need to muscle it all in one shot.