which heat pump for 24 ft round ag?

I have been through the archives, and studied heat pump info til my eyes are crossed. I was wondering if any of u know which heat pump is best for a round 24 foot above ground pool, with vinyl liner. I am in Northeastern NC, where summers are very warm, but Spring and fall can be quite chilly. I would be happy if i could extend my swim season from 6 months (April-September) to around 8-9 months...(thinking perhaps March-October/November). I have solar heat on my pool, and keep a solar cover on it whenever it is not being used, except in the hottest part of summer. I need a good heat pump, but know nothing about how many BTUs to look for, which ones are most dependable, etc. I DO know i want one with a titanium heat exchanger. Any ideas? I'd like to get the "most" for my money. I guess i need to buy one with the highest BTU rating that I can afford right? I really practically LIVE to swim, but this is all so confusing! Thanks in advance for any advice.

I also would like to know. I have a 18 x 24 above ground pool under a shade tree with a 60% shade tarp and need a pool heater. With so many brands and types of heat pump & different types of heat exchanger, which one do you buy.
One brand says life time warranty, but whats considered a lifetime for a heat exchanger. (Rigid Tools gives a lifetime warranty on their drills, and saws, etc. but then you find out lifetime means the life of a cordless drill which they think is only 7 years, not your lifetime, but they don't tell you that when you buy it).

Another brand says all titainium while another says glass coated " chemicals never touch the metal" so confusing. Which one is the quitest, which one is the most efficient, which one stands behind their warranty the best, which one uses the least electricty, which one breaks down the least, etc.

Any one have expierence with these, any knowlegeable distributors out there that really know these things? I already decided electric heat pump, but which brand is killing me.

i just ordered from poolheatpumps.com. i got a heat siphon sx3.25. marc and his staff are most helpful, and they have the best prices too! they will help you choose for your needs...honestly! they even told me the less expensive of the 2 i was looking at would better fit my needs! CAN'T GO WRONG WITH THEM!