These http://www.amazon.co.uk/RHA-SA950i-Portable-Headphones-Titanium/dp/B008JFRRYK/ref=sr_1_6?ie=UTF8&qid=1403466680&sr=8-6&keywords=rha+headphones , as a bit of a bass head your like these there flat to 16hz.
Passive speakers you need to buy an amp, actives the amp is built in. These are in your budget http://www.amazon.com/Genius-Hi-Fi-Speaker-Computers-SP-HF500A/dp/B0041QBAIA/ref=sr_1_3?ie=UTF8&qid=1403458227&sr=8-3&keywords=genius+speakers .
In-depth review of the microlabs mainly object: http://www.ixbt.com/multimedia/microlab-solo7.shtml (needs to be translated to english)
In-depth review of the edifiers object and subjective: http://www.tomshardware.de/edifier-r1280t-review-test-pc-audio,testberichte-241528.html (also needs to be translated)
A decent 2.1 for £300 can easily be done.
active speakers: http://www.amazon.co.uk/Microlab-SOLO9C-140W-TOSLINK-CO-AX/dp/B00HR1AWVC/ref=sr_1_7?ie=UTF8&qid=1403438749&sr=8-7&keywords=microlab
or smaller speakers http://www.amazon.co.uk/Edifier-R1280T-Wired-Active/dp/B00GBN50SC/ref=sr_1_8?ie=UTF8&qid=1403439011&sr=8-8&keywords=edifier ,
What about http://www.amazon.com/Behringer-SRC2496-24-Bit-Sample-Converter/dp/B0002E50J0/ref=sr_1_1?ie=UTF8&qid=1403377911&sr=8-1&keywords=behringer+src+2496 , it has coax and optical inputs and xlr ouputs so you can go balanced and use xlr to xlr cables with your monitors , I use this dac myself its great value for money.