There is no such thing as a good pair of speakers for any AVR. Speakers should be picked out first and be based on budget and the sound you like. Dedicate 3/4 of your budget towards your speakers.
Your only option is to go out and audition all the speakers you can find and see what you like. If you have already purchased the 3808 you will be fine, with most speakers you find, as it has a decent amount of power. Just try to find something in the 8 ohm range with a decent sensitivity above 90db or so.