Ok....
DBX? They are owned by the Harman group now.....I think. I found most DBX compressors are used in Live rigs, especially ones manufactured within the last 10 years. I have the 266XL, and all I will say about that is that it compresses. I use it when I mix live, and occasionally use it to get my levels to digital nice and healthy. it is basically crap though.
The original 160 is a classic, and used alot in live rigs of big time engineers, but the 160a is a different beast altogether. Seems like alot of people use it for their live bass rig. I dont know if it will be the same with synths.
Focusrite? Crap (Unless we are talking Red) All their new stuff is useless.
Presonus? Crap. Dont bother.
How about a Joe Meek optical compressor. Maybe a bit pricey, but then you could just fuck off the DBX 160a. Around $1500 AUD. Try:
MIXMASTERS
How about something from TL Audio? They are in the budget range, but probably better than Focusrite or Presonus. Something like a FATMAN 1. Probably around $1500 AUD NEW.
I know you know this, the whole might aswell buy something decent blah blah blah, and I know it is a different story when you just dont have the money. But yeah, you should just save more and buy one really nice stereo/dual mono compressor.
Good luck mate!