I haven't heard either of them. The low frequency response isn't all that different between the two speakers.

Generally, I would think that monitors would work better in small rooms. But, since you are looking for speakers that will eventually be in a larger room, I can understand your point.

I think the monitors would give you better sound in the here and now and might even sound better in a larger room.

You can find the Infinity Primus 360s on eBay for around $280 US (looks like they are comparably priced on www.kieskeurig.nl) and I think they sound much better than the JBL Northridge E80 (only model I've listened to). I don't think the E60s would be any better match to your existing speakers. JMHO