I used to own the P-5 and now have the 5.3 The 5.3 is more transparent, lower noise floor and better bottom end. If you check the specs it is even better than the P-5LE model by a long shot.
The 5.3 will give you 80 to 85% of the performance of the P-7. The 5.3 is fully dual mono front to back, the P-5 wasn't with only one transformer. The 5.3 is not a modified P-5, it is all newand does indeed have the evolution technology. Don't let the single box design fool you, it's a substancial upgrade over the old P-5 at a grat price. Hope this helps.