I would respectfully suggest that I think you can balance your funds better.
First of all, where you actually put your speakers will be of utmost importance to you...especially as you will be mixing DnB which relies heavily on thumping kick drums and thunderous bass.
In light of this, I would HIGHLY recommend you budget for some speaker stands as if you simply place speakers on a table the soundwaves will propagate through the surface resulting in muddy bass frequencies and your mixes WILL suffer. You need to decouple your speakers from direct contact with tables (hence the stands).
Personally, I wouldn't go for Mackie monitoring either but this is more subjective than objective. Don't even think of buying passive monitors - always buy active as the amps inside the speakers are specifically tailored and designed for the speakers to which they drive. Likewise, the less to go wrong the better!
Look at the Alesis MK IIs. They're fantastic for the money (?£230?). Conversely, the Audio Interface will be the direct connection from your computer you to your speakers so choosing the right one will be quite important. You need to think carefully about your needs in terms of inputs/outputs and whether or not you need audio recording capabilities before you make an informed decision on an interface. Also, are you going internal, USB or Firewire with the interface?? I personally use RME gear but that will be probably be above and beyond your budget. Think M-Audio, Mackie, Tascam and Roland. STAY AWAY FROM BEHRINGER!!!
How serious are you about your production? Do you plan on mastering as well or take your mixes to a mastering suite?
Just to give you a bit of background I own and run a recording studio and have been actively involved with professional recording both as an engineer, producer and artist for the last 10 years. Now, I teach A Level Music Technology at schools/colleges and am currently recording an album so do your best to answer some of my questions and hopefully I can give you some decent informed advice!! Afterall, I was there 10 years ago and made too many mistakes to name - why do the same to yourself if you can help it??!!!
Tom
P.S XLR is the best connector out of those as it is a locking connection and is inherently balanced resulting in less EFI from other sources and hopefully retaining a higher integrity of source audio.