I was like you. I doubted I would have more than five or six engines, but four years later I have 13. It's the nature of the beast. You see something that appeals to you and it shows up at Christmas...every time...every year. Then there's that can't-pass-this-up blowout sale you spot while surfing. Before you know it, four years have gone and you don't know where to park all your stuff. Engines don't take up all the room...it's the cars you buy to go behind them that take up the lion's share.
About the EZ-Command. It is a sedan with a twin-cylinder engine in it. It'll move the car, but only just. The EZ-Command is very limited in its features. That may not be a show stopper for you, but when I learned that it couldn't do more than change the address on a brand new DCC engine to whatever number you wanted, and blow the whistle and the other functions, I felt it was not for me. I wanted to be able to programme the momentum, alter the whistles from the selection on the Tsunami decoders I own, adjust bell ringing rates, and so on. The EZ-Command won't let you do these things. It will play all the major common functions, but you won't be able to adjust any CV's beyond the addressing ones.
There is a way around this problem, but it requires you to take the engine to a friend's house, or to your hobby shop, and have them make the adjustments to your decoder's settings. If you must do a full reset to factory defaults (it happens from time to time), you'll have to go back to your friend/retailer and have them do it all over again.
When I first got mine, I didn't really understand its power limitations. I believe it was only 1 amp...it may be more these days, or perhaps there are additional boosters available...someone else will help me out with that. But, one amp is very low for all but a tiny layout with only three DCC (non-sound) engines, each pulling a decent load. If you add grades it may be too much...not sure.
If you don't mind these limitations, and understand that it is very likely you will have to shell out more money within a couple of years at most for a more powerful and more capable system, then by all means dive right in and enjoy it to the extent possible. If you really have the self-control to deny yourself even one or two more engines within 24 months, I would be greatly admiring of that quality, and you would still be in control of a capable system. My experience, from reading what others say here and on several other forums, is that virtually none of us can resist the occasional purchase, and they tend to be engines. Before you know it, you have three or four to run and may be out of power. This is especially true of diesels when we find we want to MU them. I can't say whether or not the EZ-Command allows you to consist engines...again, someone else will have to speak up.
-Crandell