If I understand well, your receiver has Pre-Outs, but no "Amp-In". Old receivers used to have pre-outs and amp-ins with jumpers going from one to the other. That explains why someone here assumes you have amp-ins.
The person suggesting an external amp had perceived that you did not have amp-ins. In that case he was correct, if you run your pre-out through the EQ, there is no way back in for the signal: it needs a new power amp.
As far feeding the EQ through the pre-outs, the catch is that since your volume control is BEFORE the pre-out, all the EQ noise will be fed at "full volume" to the amp - you will have more background noise, in your TASCAM as well. Also, the input of your TASCAM would be affected by your receiver volume, which you probably don't want.
Another option you have is if you plan to use your EQ always on the same source. If you do, then you're in luck. You can connect your source to the EQ IN, and run the EQ OUT to your high level input of your receiver. And connect your TASCAM to the EQ OUT as well, may be using RCA "Y"s to split the signal. If your source is vinyl, you would have to get an external phono preamp.