Almost all espresso machines above entry level produce consistent brew temperature
with proper operation. For Silvia, that means temperature surfing, for E61 HX machines, it means flushing using the
water dance or the thermocouple adapter I posted above, for double boilers it means a quick warm up flush (as opposed to the variable flush amount of HX espresso machines).
One value of the site's reviews are clear, step-wise documentation of how to operate each espresso machine, confirmed by long-term use, direct measurement, and of course taste. Although I use a thermofilter and the like to shorten the "getting to know you" phase of a review, taste is a faster and more accurate means of adjusting the brew temperature. Adding a PID to your Silvia will conveniently manage the brew temperature, but in the end its LED display is just a number.
So to answer your questions directly:
Q. What machine for around $1000 brews at a more consistent temperature?
A. Lots of them, just pick one.
Q. How can the temp be measured on these more expensive machines?
A. Taste.