You are correct that you need to purchase several packages to get all of the functionality. From what you have mentioned already I would get:
1) NPM - Network Performance Monitor - Licensed per managed node in bundles from 100 to 2000, then unlimited
2) SAM - Server and Application Monitor - Lots of good monitoring for Exchange, AD, IIS, and MS-SQL. Then you can create custom monitors to do just about anything you want.
3) LA - Log Analyzer - You specifically mentioned this, I haven't purchased it yet, but that's because it's somewhat new.
4) VM - Virtualization Manager - VMware and HyperV, and maybe others...
If you are going to be monitoring over 1000 Nodes (servers, switches, routers, etc). Then you probably need a second polling engine right off the bat also, and maybe an additional web server. I say "probably" because nodes is not the actual measurement of the poller performance, but the actual numbers are more complicated to understand until you get into it for a while.
I am only familiar with the old pricing structure, but I do know there is a newer one that is also available.
There are also a LOT of other packages I would suggest (NTA, NCM, SCM, SRM, IPAM) , but that is already a lot to bite off in one setup.
I would get with a sales person (and sorry, they will hound you with deals), then come back here with any questions. Here on Thwack you can get your questions answered by both normal people who have been where you are and from soalrwinds employees who actually understand the products.