I listened Marantz PM8200 with Dynaudio Contour S 1.4 and it was excellant but not 7001 KI with 1.8 MK2
So you have good a basis to go by there but that's no guarantee that it would hold true thoughout the ranges as you know, otherwise you wouldn't be asking
Are you able try before you buy? I realise, being used, could be difficult to do if time, distance and /or an unwilling seller is a factor, but worth asking as its a sure fire way on knowing if its pleasing to your ears as that's what matters most
Had to do a little research on the Dynaudio's as i know of them, but not much about them. Well rated in the industry, quality and suppliers of driver to many known brands, Cello and Totem to name a couple. The 1.8 MK2 was around £2.2k when new and going by the spec and reviews, very formidable and have to be at that price. This suggest that an amp a class above the 7001ki would probably get better results from them, or a lower class of speakers may be better matched with the 700ki. Just mu opinion though.
The 1.8 MK2 are apparently much sought after on the s/h market and i would expect them to sound better than the RX2's you currently have. They are getting on, but if well looked after, should still do the job and properly too. So if you want them, go for it. If not to your liking, sell them on or think about changing the amp.
Out of interested how does the RX2 sound with the 700ki?