I have too tried the S4 and found them underwhelming. Of course, that's considering their price at 79.99 retail. The S3m are far less pretentious and cost under 15 if you buy them at the right time. The sound is slightly V shaped and actually performs quite well. B3P1 is not going to be 4x better than your SHE3590 since that's not how objects work. Even at substantially less than 100, the principle of diminished returns still apply, so while better, I'm sure it won't even be 2x better. Not to mention such quantification of SQ is quite impossible. The value of the B3P1 will only become apparent to you once you try them out for yourself. Are they worth the 60-70 dollars? In my opinion, absolutely. Otherwise, I wouldn't have purchased a 2nd pair as a spare a year after the first. I was quite convinced during the 1 year ownership that the B3P1 as a daily pair are quite possibly the best earphones ever made. The reason has little to do with SQ alone as my criteria for daily earphone are the following:
1. Price must be below 100 dollars. If I lose them, then I should be able to accept their loss and have access to replacements easily.
2. Comfort and fit. The shape of the B3P1 as I'm sure you've noticed are somewhat based on the IE8 and IE80 from Sennheiser. The shape is in fact a bit better on the B3P1 and are superbly comfortable.
3. Isolation - Very good with the right selection of tips
4. Durability - kevlar wires in a nice linguine form. To be frank the wiring is a bit odd, but they're still functional and well made
5. Looks - they look much pricier than they are!
Of course, SQ matters the most. That is a given. But all other things considered, most earphones don't meet my requirements because they typically cost over 100 to get the same level of performance. The shape is one which I am very familiar with since I own the IE8, and have no issue with fit or comfort. They're nearly expendable as they can easily be replaced. My earphones before the B3P1 were the quite well respected Sennheiser IE7 which I picked up for 85 dollars used. They're no longer available at that price and are irreplaceable so I ended up betting the B3P1. I owned both the TTPOD and although the TTPOD is the more fun earphone, the B3P1 is much closer to neutral and linear. The only major drawback of the B3P1 is their impedance. They need A LOT of power. Very close to full sized cans.