Question need some feedback about hosting

[Amavisca]

I am in a Dedicated Servers - Pen 4 right now and the contract with my host will be end on March. However I dont want to do business with them anymore since their server is very unstable and lack of tech support.
I am planning to move to another host and I am going to chose either: theplanet.com or servermatrix

Which one should I chose and what plan would you suggest ? I am very newbie when it comes to server stuff like this so I need a fully managed server. My forum has about 17000 user + with almos 100000 posts. User online at the same time: 250+300

Also, since my database and file are quite big, do you guys know any service that offer about moving host or i will have to do it by myself???

Thnx inadvance.

Ps: Sorry english is not my first language