Best and easiest path -
1) Build a syslog server (I suggest syslog-ng). Instructions abound on the internet for this. For this purpose, it shouldn't have to be huge - a smallish linux VM would be fine.
2) Make solarwinds do syslog, sending it to that server. (If SW can't syslog, this is a problem we can't fix).
3) Then install the Splunk universal forwarder on that machine, have it read/parse the files and send them in.
4) (and more steps mostly not specific to this task, but important, like don't forget to logrotate them and so on.)
While you can send data outbound from SW via syslog, it's not the best or most efficient method. You'd basically be crafting either
1) a single alert that sends a syslog for each data point you want exported
2) multiple alerts that send syslogs for specific types of events/data collections
(remember, alerts are queries, so you'd be banging the database with queries on a near constant basis, obstructing the ability of the database to do the thing you want - which is to collect monitoring data.)
SolarWinds has a full REST-ful API (it's on Github, look for "SolarWinds Orion API" and you'll find it) which would let craft a script that exported the data you wanted, when you wanted, with all appropriate security checks, throttling, etc in place. There's a whole forum dedicated to building this kind of stuff on THWACK.com.
If you are still committed to the syslog method, I'd just want to add a couple of other thoughts:
I'm going to take off my SolarWinds hat and put on my "I've been doing monitoring for 20 years" hat - remember that monitoring is fundamentally a heterogeneous pass time. There's no one-size-fits-all solution (hell, there's not even a one-size-fits-most solution!). While you want to avoid dealing with 27 tools that do the same thing, you are going to have a mix of primary and secondary sources of truth; of cheap (sorry, "economical") systems that do the dog's work of monitoring and pricey solutions that provide laser-pinpoint insight for a specific condition. Just make sure you're designing for the correct mix.
Hope this helps.
- Leon Adato