Question about wiring 2 light circuits with dimmers in small space

What is the total wattage of the bulbs involved? If higher than the capacity of one dimmer, you might want to try smaller bulbs, see if it's enough light, and go from there.

You can always use more receptacles.

A double switch box,or 2 gang box, should be wide enough for two devices, regardless of type, including two "standard"dimmers. Sometimes when granite or similar materials are cut, they don't quite cut enough to match the box opening. When this happens you won't have the room for wide devices, such as dimmers, which is probably why you have one dimmer and one narrow switch. You could have the opening widened, or possibly use a high wattage dimmer to control both banks of lights and just install a dummy switch next to it

If you are running close to the maximum capacity of the dimmers, putting two of them in the same box is likely to result in an overheating situation. As someone suggested, unless you need the lights at full brightness, it may be a good idea to use less wattage in the lamps.

You can get 1000W dimmer switches. One of those may fit your needs.