If it were me (and remember this is only relevant to me) on a medium to medium-heavy THS and I were starting an arsenal:

I'd go with a Cold Blood but bring the surface up to 2000 + a used 2000 pad and probably a Cobalt Vibe drilled strong with a polish.  This way I would be able to get more shell and less shell as needed.

This is my SUBJECTIVE opinion on what I'd do if it were me.  This would fit my idea of "a good two ball arsenal" and leaves you the option to supplement the top and bottom as needed.

I am dropping a pound in weight and plan to buy two new balls to start with.  What would be a good two ball Hammer arsenal (not counting a plastic ball) that would cover heavy to medium conditions.  May add a dry lane ball later.

With my old 15 pound balls, I have slower speed (about 13-14 mph) and lower revs.  I hope to see my speed and revs increase some with the lighter balls.

Thanks for the help.

You are going to need some help on the backend with the lower revs.  I would do a Cold Blood as the higher end and a Spike for your lower end.  Both balls are the newest releases from Hammer so should be pretty easy to grab each of those.

I just bought a Nail Titanium (15 pounds) which is billed as a "medium to dry" lane ball. My speed is similar to yours. We generally do not see heavy oil in the several houses in this area, so I expect to use the NT a great deal. So far, I like the NT. It is an excellent ball for the price.