Based on my research it looks like the JTR RS1 is probably somewhat better for most people than the Perlisten D212s is. The things the D212s does better would not be as noticeable as the things the JTR does better. Comparing the Perlisten D215s to the JTR RS1 the D215s is better, but the price makes it very prohibitive. Maybe if I can get a big enough discount on the D215s I would go for it, but as far as price/performance companies like JTR and Harbottle make it difficult on larger manufacturers.
Harbottle isn't really the same as JTR - its high-end luxury, extremely high performance. JTR is more budget conscious.
Their facebook page just showed a dual driver 18 inch subwoofer reaching 100db @10hz. For the footprint it occupies, its pretty impressive whilst likely having a better fit and finish than the JTR.
Harbottle are probably a league above in terms of performance, build quality, DSP control but also price. The Carbon fiber finish is great. Funk's wood finish looks like luxury furniture, especially their walnut but very traditional.
Their C18L2 is £5.1k excluding sales tax.
Their C24L2 is £8k excluding sale's tax.
A JTR is £2.6k excluding sales tax with a potential 5-10% discount.
A Perlisten D215S is £9k including sales tax but can be had for a lot less in terms of discount.
At 10hz, it'd take 4 RS1s to match the C18L2 or two RS1s stacked together.
At 10hz, it'd take 4 RS1s (or D215s) to match the C24L2 to match it and they'd have to be put into pairs for a +6db output gain.
Obviously you do pay for it. The C24L2 ends up being more expensive than a D215S - but you obviously get superior headroom and performance with limitless compression compared to the D215S's DSP based compression.