I'd agree that a higher tiered board is probably a good idea.
If your new case will support it, getting a full ATX motherboard rather than an micro-ATX board will give you the needed space between components and likely offer features not available on that mATX board like more fan headers and higher end components like VRMs, depending on the model you choose.
While not strictly "wrong", having components too close can certainly increase or complicate problems with heat, especially if there is not a significant amount of airflow through the case made possible by the presence of adequate case fan cooling.