Best small used monitors under $1000

Any Green Mountain Audio monitor such as the Callisto or Europa, possibly the Rio also

Used Joseph Audio RM7s would do it for me. 

I heard every speaker in the current Harbeth line except the P3ESR. I can’t imagine they sound bad:) I assume you are in Portugal. You may able to find a used P3ESR around $1000ish. Not in US though.

If you're willing to go the active route I highly recommend the Airpulse Model One's - $995.00   I've had mine for a couple of weeks now and Just a great all around speaker for the price and then some. I'm going to be doing an updated review on these soon