I did my 7x12 a few years ago.
For the controls I would recommend you use
2x Gecko G251 (these were not made back when I did mine)
1x Keling KL- 4875 Power supply
2x Keling KL23H276-30-4A
1x Keling C10 breakout board.
You could probably fit all that into the space left by the Gear train.
If you buy a Homann speed controller, you can also control the spindle from the CNC software.
You can get break out boards from lots of vendors, also Vexta motors could be used, and a PSU you can make yourself, so I have just used Keling as an example here. This stuff is pretty cheap, so rather than mucking around trying to save the last couple of bucks, making one order with an outfit like Keling will probably save you a bunch of time.
For software, I use TurboCNC as I am running it on an ancient Pentium laptop. If you have space for a desktop PC, then Mach 3 seems to be the most popular control software. EMC also has a strong fan club, but will need a bit more computor skill to set up.