I would not sell your P25 until you are completely satisfied with whatever turntable you buy, should you decide to go that route. I know of a few people who had sellers remorse after being let down by their "new" purchase. The P25 was replaced by the P5 so you basically have something with some degree of rarity.
The P7 will definitely sound different than your P25 but will it satisfy you, given the price difference. I prefer the P5 as the best buy in the Rega line. I own a P5 and a P3/2000, although I outfitted my P3 with an RB-700 tonearm a few years ago. I know someone who is considering selling his P7 because he is so distracted by the P7 platter.
The P7 will definitely sound different than your P25 but will it satisfy you, given the price difference. I prefer the P5 as the best buy in the Rega line. I own a P5 and a P3/2000, although I outfitted my P3 with an RB-700 tonearm a few years ago. I know someone who is considering selling his P7 because he is so distracted by the P7 platter.