If you decide to buy tanks, steel HP100's are ideal for all-around diving unless you are very short or light of frame. More air + less buoyancy is a winning combination and if you're doing any sort of public safety diving, you'll likely be in a dry suit where reducing the weight required is important. For gulf of mexico diving, HP100's are just about right for most 60 - 100' dives on NITROX to provide plenty of air to reach NDL times and make a safe ascent (once your breathing rate settles out). Everyone that I know who dives regularly here owns one or more sets of HP100's.