I would go with digital ballasts... Lumatek or Quantum
Why lumatek or quantum,what benifits do these 2 brands offer that warrant reccomending those specific manufacturers.
Both brands are the most expensive on the market,both also have munafacturers that claim superior performance vs competitor products,while claiming superior performance the brand Lumatek has been plagued with extremely high ballast failure rates.
Why are you reccomending the most expensive manufacturers when the op is looking for a deal,especially Lumatek which is a product with a proven high total failure rate ? The internet is full of unhappy lumatek owners.
Most of the hype surrounding lumatek & quantum being superior gear is spread by unscrouplous hydro shop owners who only care about pushing the most expensive gear,& by shills who work for them & push their gear on forums.
The link above from HTG offers quality gear at affordable prices & their in house brand has a great no questions asked replacement warranty,they are the largest imdependant hydro store in the USA & have great customer service,before & after the sale.
My review & reccomendation is based on my personal use/ownership of over 20 various wattage ballasts,both magnetic & digital alike,my htg digital ballasts have functioned perfectly,some digitals as long as 6 years trouble free.
I did have one problem with htg though,i ordered 24 of their in house brand 600 watt hps bulbs,they shipped 18 hps & 6 mh conversion bulbs,i called & complained about the 6 wrong bulbs & they appologized & sent me 6 hps bulbs,they let me keep the 6 conversion bulbs for my trouble,they are a kick ass manufacturer & i stand by my review of their products.