Thus far, I've used two brands of Discones over the last 30-some years, the 1st being the Radio Shack one from the 1980's. That worked very well on VHF high and UHF, and was my 1st dual band antenna for 2M / 440MHz. Terrible on VHF low band, but that was to be expected. I had that one over 30ft in a large fur tree, and the aluminum GND radials broke off of that one during +80MPH storms. A decade ago I bought the $100.00 Diamond Discone, with tunable 6M VERT stinger. I'm using that for 2M, MURS, 222MHz, 440MHz, but wouldn't match 462/467MHz GMRS. Also, 6M FM 52.525MHz. Again, about 30ft up on masts. (This time.) I'm in the bottom of a river valley, and that just less that unity gain helps to get me out of this valley. Anything higher gain just bounces back at me off the hills. (And yes, I've tried it and proven this to myself.) The Diamond also survives +70MHP storms and those stainless steel GND radials seem to hold up well. So, it sounds like that you can't go wrong with the Sirio discone. As far as a preamp? TV amps may be wide band enough for ya, and some have switchable FM traps. As far as not RX'ing IMD? How close are you to pagers, TV stations, and EMS / fire / police dispatch? So far, no IMD for me being only 1 mile from a 1MW UHF DTV transmitter here, but I do get some UHF pager bleed through. So does a friend of mine a few miles away.