I think it depends on what gaps you are looking to fill in your collection. You do have a broader range than most (meaning little overlap), so it's really just a question of what you feel is missing.
- The Quick Mod is going to be the highest gain of the Marshall bunch and most unique as well. I hardly think of this module as a mid-gain module by any standard and that's not it's strong suit IMHO. If you drop tune, this is not my first choice module either.
- The D-Zilla is a great mod and very versatile. It has an open, organic clarity to the midrange that is truly where this mod shines.
- The XMG+ is a unique design and great for modern metal with a broad range of tones for that genre. The switches are all designed to be used in conjunction with each other. To truly appreciate the palate of tones here you need to pay attention to how they interact. It's also whisper quiet with no gating, just a sound original design from the ground up.
I would never recommend dismissing any design based on how "authentic" it is or is not. That's a sure-fire way to miss out on a lot of fantastic tones you might really fall in love with. Remember: these modules have limitations to work within and the first gain stage is ALWAYS in the amp itself. No mod to a module alone is ever going to be 100% authentic (we always strive to do the best job possible of course), but it may certainly kick major a$$!
Happy Holidays and enjoy your new toys,
Rob