Suggest an ad server company?

Roku did supply a list of companies, but no actual contact info and most of the companies just don't respond. The ones that have required a larger audience similar to what Roku requires before being accepted. 

The list Roku provided was:

SpotX
Telaria
Freewheel
AOL
LKQD
Beachfront
OpenX
Rubicon

My only replies have been:

Freewheel won't tell me how much volume they need other than "We can revisit this conversation once your audience is there but right now its not close to the 25M impression ballpark", which I thought would be 25 thousand ads per month minimum. My research showed "An impression is when an ad is fetched from its source" and The "M" in CPM represents the word "mille," which is Latin for "thousands. I provided my math to show I was well over that threshold, but FreeWheel said it was short of what they needed, but would not clarify further even as I attempted several times to try and understand their terminology and math and contrast it with my provided calculations. My formula was 16 ads per hour x the number of hours per month of streaming. Their use of "impressions" may be different as the rep directed me to an old article that referred to web page impressions and not streaming media. My contact there was Patricia Whitney (pWhitney@freewheel.com). Try giving her an email and if you get any clarification please let me know. 

SpotX got back with me and were much more clear on their minimums. "We will need to see a minimum of 1 million monthly video ad calls from your inventory". My contact there was Derek Quinn (dquinn@spotx.tv).

I went off list and heard back from Verizon Media, but after playing email tag I didn't get a response for the actual meeting, but I intend to follow up again as the rep (Daniel Herrera daniel.herrera@verizonmedia.com) seemed like he was open to a call. 

That is literally all I know about the subject. I contacted every other company on the list without any replies. Let me know if you have more luck than I did.