I've been though a few. I started out with a custom made ~800btu/h chiller with a large cooler and a sump pump. This had a good size reservoir but the pump generated quite a bit of heat and 800btu/h isn't enough.
I then went to a smaller 1/6hp beer line chiller which had a smaller 3gal reservoir but a better external pump. This worked pretty well but when cold crashing my 14gal conicals it ran nearly continuously.
I have copper coils around the outside of the conical, if you have an inside coil it may cool easier.
I now have an older 1/3hp. ~4000btu/h 14 gallon beer line chiller which is working ALOT better.
My advice is get something atleast 2000btu/h+ and reservoir size dictates how often the chiller will cycle. I used PEX for my manifold for ~1-2 years now without issue, just keep in mind glycol has lower surface tension than water and will find leaks easier, so make sure to carefully leak test everything!