SRO 2000 and Diablo 250 would both work very well. SRO is a little cheaper, but rated a little lower. I prefer the single large pump on the SRO 2000 as opposed to using 2 pumps on the Diablo 250.
If you really want a low price get the NWB200, it's less than $300 and rated for 250.
I use a Diablo 160 on my 75g mixed reef. I'm very happy with the performance, it gives me a consistent skim that is easily tuned with the gate valve. The output pipe is 40mm so to plumb it under your waterline it requires a little modding. I too 1.5" schedule 26 pvc and hit it with a heat gun to make it into an adapter and plumbed off of that. And even with a silencer there's a pretty intense sucking sound on the air intake, a couple feet of hose attached to it really quiets it down.