Hi bench43
Since you picked up your Pro4.5 used I would look for the EC-100 or EC200 from the same era. These speakers were built around 10years ago. Other options may include ECC, Encore.
Look on eBay or something similar to locate these.
Remember that timbre matching is key to have the tonality consistent with ALL speakers. Don't mix and match from different manufacurers as the synergy created from single manufacturer would be lost. A loudspeakers' sound characteristics are based on the designer's beliefs much like a culinary chef. You may use the same ingredients as everyone else but everyone's taste different. These days there are a lot of good speaker companies out there, just try to keep the same flavour throughout.
BTW the Pro4.5's were a good speaker then and still good now!
