Sound Stage Network doesn't have measurements for the Studio 100 but they have the
Studio 60 v5 (this is for the listening window):
Compare that to Arendal's measurements for the 1723S:
Arendal may be employing a little smoothing on their graph but both speakers are fairly neutral. The Studios have a little dip around 1.5k while the Arendals have a little hump at 1.8k. Hard to say how noticeable that would be in your room. The Studios still get pretty high praise in the Paradigm forum on AVS Forums and the subjective comments are that the Studios are fairly neutral compared to later Paradigm offerings which had more of a signature sound. The quoted FR specs on the Arendals are +/- 3dB while the Studio 100 is +/- 2dB and the sensitivity is 89dB for both.
So, judging by the numbers alone this may be more of a lateral move.
James reviewed the Arendal Monitors here. Great dynamics but it's hard to say how the vertical and horizontal dispersion of the Studios compare. I have the Studio 20v5 and CC590 centre and I love the centre. That may be the one drawback to the Arendals. The centre is a MTM design while the CC590 is a 3 way which offers better off axis response.
I am surprised that your wife does not like the rosenut. I always found the rosenut finish beautiful.
The curved metal grills on the Arendals do look pretty cool though and it's a more contemporary looking speaker. FWIW, I came very close to ordering a pair of 1723 Tower S speakers last year. I think it's a great product and while not a huge step up from the Studio 100 they should compare very well.