The most active way to play this line is play 8...dxc4 followed by 9...c5 immediately challenging the centre.
This is the typical develpment for Black.Pay attention to the Rfd8-Bd7-Be8 manoeuvre.
If white is more ambitious then he will avoid 10.dxc5 and will accept an isolated pawn.That is the best way to play for a win.The only problem is that Black gets a lot of winning chances too.
If white at some point soner exchanges at d5 the knight is better placed at d7 for the typical anti-minority attack manoeuvre Nd7-Nf6-Ne4-Nd6.The following games are typical.
Here is a position I sometimes get in the queen's gambit declined:
In this position I think the normal way to play is 1...Nc6 with the idea of ...Ne7 and ...Bf5 trying to get some kind of good exchange position. For example 1...Nc6 2.cxd5 exd5 3.a3 Bxc3 4.Rxc3 Ne7. The idea is that 5.Rxc7 Nc6 traps the rook. So Black can play c6 and Bf5 freely. But this doesn't look as active to me.
So I thought about 1...Nd7 instead with the idea of ...b6, ...Bb7 and ...c5. This looks more dangerous because it's slow and pretty easy for White to try and stop it. I looked at 1...Nd7 2.cxd5 exd5 3.a3 Bxc3 4.Rxc3 c6 5.Be2 (5.Qc2 maybe?) b6 6.Qc2 Bb7 7.b4 Rfc8 8.b4 and got this position:
Is it possible for Black to play this way?