well in theory, a 1500 watt motor would pull 13 amps at 115v. Ridgid makes a good 14 gallon one that is 6.0 hp, which roughly turns out to be 1320 watts

Sure, but the electrical draw is one of the least important aspects of a shop vac, as it tells you pretty much nothing about how the tool will perform. A low efficiency, crappy tool can easily draw that much, a much better performing high efficiency tool might draw considerably less. I'd worry instead about CFM, static pressure, noise, filtration media (e.g. HEPA options), ability to switch on when a plugged in tool like a sander is turned on, convenience of emptying, whether the casters will roll over common obstructions in the shop (like the vacs' own cord), whether there are adapters to connect to your tools, and noise again. I recently replace my old vac with the Bosch vac090 and it's fantastic-- sucks like crazy, very quiet, great wheels, HEPA filtration. I have no idea how much current it draws, though it must be much lower than 12-15 amps as I can plug my big 6" random orbit sander into it and run both on a 15A breaker without popping it. It would be very irritating if that were not possible. Lots of folks love the Festool and Fein vacs, and the Ridgid has fans as well.

There's no doubt that companies like Bosch, Festool, and Fein make great vacuums (dust extractors) but for the needs of most homeowners, they are a pretty substantial investment. Not only is the vac expensive so are accessories and consumables. Festool, for example, charges $88 for their "compact cleaning kit" which includes the tools most people would use for general cleaning. Fein gets about $6 each for dust bags.

I have been looking for a decent quality, general purpose vac that doesn't require a second mortgage. It just needs to do wet/dry pick-up, no blower, power port, or anything else. Preferably one without a huge footprint and accepts standard 1.5" and 2.25" accessories. I'd also like to use a Gore CleanStream filter with it.

And it MUST be able to handle whatever debris has managed to accumulate in my garage since it's cleaning last spring - leaves, small twigs, pebbles, etc. without constant clogs.

I think you'd like the Ridgid, but the classic Sears vacs will also do what you need. Both have CleanStream filters available. The main downside to these machines is the noise, so do your hearing a favor and get some earplugs. With that caveat they are great values for occasional use. If you need to run one for hours at a time and need to worry about long term exposure to very fine dust then the Bosch, Festool and Fein machines begin to earn their keep. After using Sears vacs for 30+ years I'm perhaps overly enjoying being able to hear myself think when the shop vac is running.