If you are looking for professional hosting the best approach is to write exactly what you want in a numbered list and mark each item as absolutely necessary or a nice to have. Think about the availability, backups, firewalls you want etc - Rack space won't give you a guarantee of more than 95% for a single box and if you want 100% we are talking 20x the cost and a solution mirrored across multiple data centres. Then send your requirements to your shortlisted suppliers giving them two weeks to respond with a statement against each one of your points. This makes them do all the work and makes it easier to compare.