TMX can easily be as fine grained as APX25 (I think Agfapan 25 is an older product, and Agfa 25 is a developer) but with VERY different image quality. Disregarding the granularity, I think Pan F Plus or Plus-X is a good candidate for the replacement. Grain and sharpness can be made up for by upsizing the format and/or using ascorbic acid version of D-76 as I call D-76Ad (formula found in my old postings here or on my home page). With D-76Ad, I can blow up 35mm HP5+ to 11x14 and have to get my eyes 6" from the print to barely see the grain, with proportionate sharpness.(posted 8216 days ago)TMX can be very good, but I suggest using a dilute developer. I can't see grain on 11x14 made from 35mm TMX processed in accutance version of my formula. I get excellent sharpness, but the way highlight and shadow come out is quite a bit different from that of APX25.
But I don't really care about grain. I usually shoot 6x6 or 6x4.5 and blow up to 10x10 or 11x14. I already decided not to look for a replacement for APX25, which I never used in 35mm anyway.