There is a strong (not absolute) corelation between good affiliates and good bookies.
For a small website there is no need to have full offer of bookies. Bet365 is the best option for tennis. Other good recteational tennis bookie is Unibet (streams same as Bet365).
Besides that the other bookies should offer something that Bet365 does not and therefore it should be:
Betfair (tight in game spread; exchange)
Pinnacle (low margin; now offer challenges)
5 dimes (for US traffic; challengers in parlays)
Really no need to stick with 2nd string bookies.
++++++++++++++++++++++
As for Coral. I like their approach, that one can feel human and not robot there, but 2months ago they released live odds banners (tennis/soccer/racing) and they still DO NOT WORK. 1st issue is that they are on default switched on racing and there is no option to show on default tennis or soccer. 2nd problem was that soccer and tennis feeds were empty. They are now filled in but WITHOUT ODDS. And on the top of that Anthony/Coral stopped responding to me.
If you talk to God, you are praying; If God talks to you, you have schizophrenia.