The Seller would want to know that you are still interested.
You should beat a path to the Listing Agents door:
Did you already do a CMA so that you know the true Value of the house?
Has it been long since then?
If you were at the Value before, I would recommend adding $500 to the Offer.
If you weren't at the Value before, I would recommend getting there, if you want to buy it.
"Low Ball's" won't work anymore.