If you want least expensive and to order from the US, go blackstar.
If you want least expensive and don't mind ordering from overseas, go Apollo.
If you don't mind spending 1.5-3x the cost of blackstars for the same wattage to get the better warranty, etc, definitely check out some of the higher end options but be sure to go with someone tried and tested not the latest gimmick with magical promises and no actual COMPLETED grows you've seen.
I went with blackstar