the record spot:Hi and welcome to the forums. Sounds like the dimensions of the speaker are the critical thing here going by the upper case...! No mention of budget as Graham mentions and likewise, no idea how these would match your gear, but Neat's Motive 2s might be worth a look as they might tick the right boxes for your space requirements. I don't think the Marantz player and amp you have are on the bright side and were
very well rated in their day, so this could be worth a look. Review below, expect to spend around £900-odd for them though.
http://whathifi.com/Review/Neat-Motive-2/
If that's a bit keen and you want to spend less, try finding something on the secondhand or ex-dem routes; you'll pick up a bargain and if you go via a dealer who specialises in this you'll get their support and sometimes a warranty too. Jordan Acoustics and Audio Emotion (both up here in Scotland) offer up to 5 year warranties on their secondhand kit (in many, but not all, cases).
The OP has already stated they are looking for pre-owned gear.
They mention S5e's which go for about £500 second hand so your suggestion of Neat Motive 2's is likely to be twice the asking price of Spendors.
Might I suggest the Totem range (Arrow etc)