You're doing exactly what I would recommend.  Continue mining with the Titans while also keeping an open ear for any buyers.  Selling and getting back a small percentage of our money now is better than having the Titans sitting around doing nothing in the future.

$1500 of Bitcoin right now is about 5.6 BTC.  I believe each Titan was originally ~20 BTC.  So, with this sale, we're looking at getting back about 25% of our investment for this Titan.

In a perfect world with no energy costs and perfect 300Mh/s per Titan, a Titan would generate about 0.056BTC a day. So it would take a Titan about 100 days to generate the same amount of BTC (again, that's in a perfect world with no electricity costs or speed/difficulty variances).  So yeah, I think selling was the right call there.