The B&W 702 S2 are pretty efficient speakers and aren't hard to drive but their impedance will drop to around 3 ohms at certain frequencies around 100 Hz and below which will make it hard for an amplifier.
Depending on how big your listening room size is and how loud you would play your music. Your Marantz PM14 S1 will probably do just fine. If you want to add an external power amp for your B&W 702 IMO the Rotel RB-1582 Mkll will be a perfect choice for your speakers. Rotel and B&W have great synergy together and are meant to be paired together.
I would also highly recommend the Classe Sigma Amp2 stereo power amp for your speakers. Classe & B&W also have great synergy together.
B&W voiced and tuned their speakers using both Classe and Rotel amplifiers.
The Classe Sigma Amp2 is a better amplifier than the Rotel and it retails for $3500 while the Rotel RB-1582 Mkll retails for $1600. These two amps have same power output ratings 200 wpc @ 8 ohms and 400 wpc @ 4 ohms on the Classe Sigma Amp2. The Classe Sigma Amp2 is a class D design and is Classe's entry level series, whereas the Rotel RB-1582 Mkll is a class AB design.
Or alternatively you can look for a used Classe Delta CA-2300 stereo power amp in after market like here on Audiogon. This amplifier was discontinued last year and can be had at discount nowadays.
The CA-2300 is a class AB amplifier and is a Delta series amplifier from Classe and sonically and performance wise will be a step up from the Classe Sigma Amp2. Its original retail price was $7k but since it has been discontinued nowadays you can find a used one for maybe around $4k or less. The Classe Delta CA-2300 is a superb sounding amplifier.
I highly recommend it for you and it will sound great on your B&W speakers.
Anyways, you might want to try driving your B&W 702 using your Marantz integrated first and see how it is. You might not need an external power amp after all. Your Marantz integrated is a Marantz Reference series line and would sound and perform better than regular cheaper Marantz line.
Btw, the B&W 702 S2 are awesome especially for the money.