Little wonder that the internal speakers have more bass than the FR1.7s, which are normally used only for manual channels in a Rodgers installation.
As to your question, the typical answer on this forum or otherwise is that used organs are rather hard to sell at any price. (How well I know this, as a tech with an inventory of perfectly good church organs awaiting buyers!) Yours might bring a little more than some, since it is (1) digital, (2) not terribly old, (3) MIDI equipped, (4) comes with the PR-300, which contains a not-too-shabby Roland sound module in addition to the nearly worthless floppy disk sequencer.
We have occasionally been able to sell (at retail, with delivery and setup included, along with a warranty) a used two-manual of similar vintage and features for between $3K and $5K. However, that is a RETAIL deal with all the extras I just mentioned. You are selling an organ "as-is where-is" without any value-adding extras, and the buyer is taking on the risk that it might actually need some repair, even though it is now functioning. This series of Rodgers organ has a pair of capacitors on one of the main boards that are known to leak and fail, sometimes destroying the entire board (that costs nearly $1500), and if this one has not had those capacitors replaced already, your buyer is indeed taking on a risk.
I'm just saying all that to let you down easy.... You might be able to put it on ebay and get $1000 or so for the whole setup. If you happen to attract two or three active bidders who really want it, you might see the price bid up more, perhaps quite a bit more.
The best way to find out is to list it on ebay, which is free most of the time, might cost a few dollars at the most. You might try an opening price of $1000 and see what happens. It may not get any takers first time around, but if not, lower your starting price and re-list it.
That's about all the advice I can offer. Good luck! Would make someone a nice home organ.