Sols are around 399 a piece same with the hydra depends on what look your going for  . I will be using 2 over my 48" tank . I have one over a 3' but that's not enough .
Although I would really like to know if I should upgrade my sols 

 and buy a hydra  and have two hydras instead ... Hmm 
O yah and sols are easy to upgrade to the next generation