I'll offer up my 2 cents as somebody who probably researched almost every brand there was.
I am assuming you have no automation? Here's a simple version of how I would break it down.
1. If you have automation, buy the system that goes with your automation (if you can afford it and price is relatively reasonable). You will thank yourself down the line.
2. If you do not have automation, buy the circupool.
In my case, I had automation through hayward and I was basically 50/50 on buying circupool or hayward. Finding a good deal on the hayward finally was enough to make me get it for the automation and I'm very glad I did it. Love that it syncs up with everything else and that I can control it remotely. If your pentair happens to have automation then you maybe look at something like the pentair ic40.
In your case, without automation and the fact that you already have circupool, I'd honestly stick with circupool. To me you have 2 options. Option A would be just buy your cell replacement if your panel is still good. It'd take 2 seconds to swap it out and all is well. As others posted, they are correct that the 30 is a little undersized for your pool, but we are talking $450 to make you last years down the line. If it were me and I was relatively happy with how the rj-30 was producing, even though its undersized a bit I'd just buy the replacement cell, unhook my old cell, rehook that new one in and call it a day for $450.
If the entire RJ-30 needs to be replaced, then absolutely I agree go with a 40+ size. Your options in that case would be the edge-40 (which I was really close to buying), RJ-45 and RJ-60. With today's current prices, I would honestly say splurge and do the RJ-60 and here's why......Money. As of today (probably through April 3), here are prices. I'll link to the pages where you would click the red button that says "Add *larger size model* for $20 more"
1. Edge 40 would cost $1210 after discount (
CircuPool EDGE-25 Salt Chlorine Generator | Discount Salt Pool )
2. RJ-45 would cost $1299 after discount (
CircuPool RJ-30 PLUS Saltwater Chlorinator | Discount Salt Pool )
3. RJ-60 would cost $1399 after discount (
CircuPool RJ-45 PLUS Saltwater Chlorinator | Discount Salt Pool )
So for basically $100 more you can get the RJ-60 and get near 4x the size of your pool which will last you a very long time. I priced out the RJ-60 last year when I bought mine and it would of been $1710 at the time....so the discount specifically on the RJ-60 is very good right now.
So to summarize, here's the short version of what I would do. If the RJ-30 panel is fine, spend $450 from the link mknauss provided above (
CircuPool RJ-30 Replacement Salt Cell | Discount Salt Pool ), replace the cell and call it good. If you have to look at a whole new setup....I don't think you'll find a better deal than the RJ-60 right now.