I added them earlier this week. Visit the review again and you'll see the Windows Experience score and PC Mark Vantage benchmarks for the 1.6GHz/ATI model next to the 1.3GHz/Intel scores.
If there are good coupon offers (HP has been good with those in the past few weeks) you might be able to score the 1.6GHz for nearly the same price as the 1.3GHz. That's what I did, and obviously it's worth it for nearly no additional cost. If money is tight and there aren't any more good HP coupon offers, then I'd say the upgrade to ATI graphics is more important for performance that going from 1.3 to 1.6GHz. Avoid the recently added Intel 1.3GHz CULV SU4100 CPU option-- that's a dog compared to the SU7300 on the quick ship model.