Yep there are a couple huge threads on rc. 350w of t5 lighting equals 500w of mh lighting.
http://www.reefcentral.com/forums/showthread.php?s=&threadid=679852&highlight=t5s
This is lit by 12 t5 tubes, (860w of lighting) and looks stunning
http://www.reefcentral.com/forums/showthread.php?s=&threadid=700454
T5 only loose 20% of their light output throughout their life (20,000 hours) although most people say they last 12 months in aquaria use.
MH loose 40% and have a large drop, 20% within the first year and a large colour shift (just look at warehouses and car showrooms, some of the bulbs are different colours.)
T5s are slightly more efficient 80-90 lumens per watt where as MH are 70-80 lumens per watt.
They light the tank evenly, mh are pinpoint light source.
I would upgrade your lighting to 6 t5 tubes. Make sure you get good reflectors, since they will increase light output by 50%. (flat reflectors reflect light from the rear of the tube through the tube and so it looses some light intensity. The more advanced reflectors are W shaped which reflects light around the tube.
As for RO units they start at £45 for a 35 gallon unit.
http://www.ro-man.com/shop/index.php/cPath/22
These are great, I have 100 gallon unit with tds meter.