The Imat is a good machine, but I guess it depends what you are looking for. *Look at Alan Frews comparison of the two machines and their construction; I think the Silvia boasts a better internal construction (boiler, plumbing etc).
I looked at the Imat when I was shopping around...it has the normal Italian quality control; lots of sharp edges...(the Silvia has them too!)..but you can pull a decent shot from it.
The pause you talk about with the Silvia is known as `temperature surfing. *Do a search on this, and you will find many opinions....for me, I just pull the shot when the temp light goes out, so maybe I am not getting the optimum extraction *:-/ *But I like it * ::)
As far as the Combi goes, I personally would keep saving a while to get a better grinder. *Having the bean hopper right next to the boiler tends to hasten the beans staling process..they get too hot. *:-/
If you have your heart set on a Silvia, make sure you shop around a bit...the prices vary considerably..
Happy espresso adventures....
P.S. - Yep you are right...you cant get a tall mug under the Silvia...or a big jug under the steam wand come to that...but you live with that - they are a very nice machine!