I would guess that a decent grinder can make more difference than a coffee machine in that price range. *It could still hinge on the machine however if it has very little ability to deliver a good shot.
There have been reports of the sunbeam grinders not grinding fine enough even with some modification so I would suggest that getting a second hand Rancilio Rocky would be the way to go. *That way, when you get the chance to get a nicer machine, the Rocky will allow you to make some good espresso :)
You might be able to pick one up for about $250-350 depending on the person selling it.