Welcome to the boat mate.
Congrats on getting to the point of upgrading your game.
I play TMO 2.1 and really enjoy it. The DD's are a bit tougher than stock but you can handle them with a little practice, be prepared to get sunk a few times. Much better game play than stock but can be intimidating at first.
FOTRS is a good step up from stock and might be a good transition to TMO.
RSRD is much more realistic shipping and Task Forces but you have to know where to find stuff so study historical events as they are all in there.
With JSGME you can switch between mods fairly easily so you can see what tickles your fancy.
Good luck and good hunting
Magic