As far as what you need... .
EGT/Pyro same thing
Boost 0-40 or 0-60 depends on how many BOMBs you plan on in the future, but a new boost gauge is cheap to upgrade. I got 0-40. Don't need vacuum.
Fuel Pressure 0-30 is ideal I think. Any more is too much, any less isn't enough. Unless you could find a 0-20 or something, but generally they are 0-30 or so.
Tanny temp if you have an auto.
Mechanical vs. Electric is kind of your preference. Electric can be more expensive. And easier to install. Mechanical some say are more reliable/accurate.
I don't personally like digital, but can't comment on the quality of the x monitor.
I just put in ISSPros and am so far happy with them. They match stock almost perfect. They are a combination of mechanical and electric. EGT and transmission temp are electric, boost and FP are mechanical. There is a pic of my ISSPros in my gallery, before they sent me the new ones with orange pointers. Do a search for gauges on here and you'll have enough reading for hours.