Why don't you build a raised bed and fill it with soil and amendments? Seems like it would work.
I also can't see how a tiller would compact the ground.
There's a little problem with the big issue.....cash!
You could always go up. Raised beds will give you the depth without the backache. I did that last year, and if you put the right soil in there it should work pretty well. If you can go down about 6 or 8 inches into your local soil, and build it up about 8-12 inches, it may be an option.
Soak the area with some water, it helps a lot.I have been out there with a pickaxe, maddock, shovel, and my Mantis electric tiller and I am tired.
I worked about 90 minutes out there and dug down to about 12" or so and about 4' long on the first row and I am tired.
Wished I had one of those hydraulic tillers so I could just go to town on this small garden area.
I used to operate heavy equipment so this digging by hand and a small tiller is not my favorite way to do it.
Yesterday I got down to an area that I couldnt get the spading fork more than an inch down. Lightly watered the area and had a beer, went back at it and could get about half the fork down in it. Works for me.I don't want to have mud as it's much harder to work in especially with a tiller.
I could soak it and wait a couple of days but I want it done ASAP as the seedlings are about ready.