I am not familiar with the classe' sp25. I currently own a pair of NHT 2.5i's. I am using an all tube amplification set-up consisting of ARC SP-8 pre-amp and ARC D-115Mk 2 amp. I have heard the NHT 2.9 in the showroom with Krell gear and I can tell you for a fact that a good POWERFUL tube amp works better. Don't however sell yourself short on power. At least 100 watts should do the trick. You need it with the NHT's. I am currently thinking of upgrading to the 2.9's. Have owned the 2.5i's for just over 2 years and they are really singing. I love this design but one thing is for certain to get the best out of them is to use the best amplification you can. Also careful cable matching is a must. I have heard several knocks on the NHT's and they are unwarranted unless the associated electronics are not excellent. These speakers are not very forgiving and will reveal any deficiencies in front of them.
