Howe has gained promotion from League One, then from the Championship, then survived in the Premiership, then thrived in the Premiership. Largely with the same team he had in the lower leagues.
Whatever you think of Wilders achievements, you can't not be impressed by Howe's achievements - even if you don't want him as Everton manager.
Silva winning the Greek League and getting Estoril into Europe doesn't really compare (in my humble opinion, of course). His 'achievements' with Hull and Watford since aren't all that impressive and it does make you wonder why he was given the job in the 1st place.
Think it's laughable that people turn their nose up at the suggestion of Howe. He'll walk into the Spurs job when Poch leaves and he'll do great.
So who are 'mid-tier' managers?
This is what I was talking about earlier. We're not going to get Mourinho and managers in that bracket - ala Allegri. Because the club appear to be all talk.
By my reckoning, a very strong 'mid-tier' manager who will eventually get a 'step-up' would be Howe.