If you want to keep the Jolida with the JL sub, I think you'll have to have the Jolida modded to add a stereo pair of line level outputs. If I were you I wouldn't get frustrated at JL--or even Jolida. As Kal said, each vendor makes its decision of features based on market demand and to make the unit more affordable. Putting speaker level inputs on subs adds cost that few people will use. The same goes for lower-priced integrated amps.
I used to use an Onkyo A-9555 integrated amp. It's a nice-sounding unit, but has no preamp outputs, and if you use the headphone jack, it automatically turns off the speaker outputs. Otherwise I could have used a stereo phone plug to RCA stereo adapter cable to use a sub.
But it wouldn't do that and I moved on. Now I use separates and my last two line stages have had two pairs of line level outputs. But there are plenty of integrated amps at every price level that have a pair of line level outputs. Audio Advisor has a Vincent Integrated for $399 (marked down from $900) that not only has preamp outputs, it has a USB port and a built-in DAC. So does the NAD 326BEE at $549 and many others.
Also, the current production Jolida JD302BRC or CRC integrated amp also has preamp outputs.
I used to use an Onkyo A-9555 integrated amp. It's a nice-sounding unit, but has no preamp outputs, and if you use the headphone jack, it automatically turns off the speaker outputs. Otherwise I could have used a stereo phone plug to RCA stereo adapter cable to use a sub.
But it wouldn't do that and I moved on. Now I use separates and my last two line stages have had two pairs of line level outputs. But there are plenty of integrated amps at every price level that have a pair of line level outputs. Audio Advisor has a Vincent Integrated for $399 (marked down from $900) that not only has preamp outputs, it has a USB port and a built-in DAC. So does the NAD 326BEE at $549 and many others.
Also, the current production Jolida JD302BRC or CRC integrated amp also has preamp outputs.