My Hayward T-Cell-15 just went out after 10 years. I'm looking online for a replacement but it is confusing because I see such a huge range in prices. Obviously, I don't want to spend any more $$ than I have to but I do want a reliable replacement. Are the Hayward-compatible knock-offs any good? My system is Aqua Plus (the manual says for model AQL-PLUS and AQL-PLUS-20). Any suggestions or advice?