D201GLY2A or Athlon LE-1620? Upgrade or Downgrade

I've been mulling over getting a modest upgrade for weeks now. Upgrade is a misnomer though, as I have been thinking about getting an Intel D201GLY2A. All this thinking about getting a low-power processor has got me wanting a processor that can cut my energy consumption to a lower rate. Certainly, at this point any other fairly modern processor would outperform my current Sempron 3000+ in terms of performance-per-watt. I have come across information online that may influence my decision to stick to the AMD platform. Undervolting seems to be a viable option for cutting power consumption. As far as I can tell, Powernow and Cool'n'Quiet aren't supported by my current processor, so undervolting my current rig might not be all that feasible.

The dilemma for me is picking a processor that will give me better performance-per-watt while keeping my PC relatively flexible. The Intel D201GLY2A saves on power, no doubt. But it does so at the cost of hobbling how flexible your system is when it comes to adding components. Memory is limited to 1 slot capable of taking only 1 Gig of RAM. There is only one PCI slot. No provisions for adding a video card, should I want to in the future. I'd still like to maintain a certain level of flexibility when building systems, so going for the D201GLY2A feels like a downgrade. I also doubt it would work with virtualization effectively. I've taken an interest on virtualization only recently and would like to experiment with it some more.

So right now, I am thinking of upgrading to an Athlon LE-1620. That processor gives me a lot of headroom, with a GHz performance jump from 1.6 to 2.4. Switching processors will also lower the TDP from 62 watts to 45 watts. Adding Cool'n'Quiet and the tickless kernel will increase the efficiency as well. The AMD Sempron LE-1150 is my second choice. It's TDP is also 45 watts, so I'm looking at the same kind of power savings coupled with a less dramatic jump in processing power. The downside of the AMD Sempron LE-1150 is that it does not support virtualization on-chip. I'd be stuck with VMWare Server. I'd been wanting to try KVM for a while now because it is much more efficient in handling system resources. Anyway, 20 watts is a lot when considering the long-term. Both AMD processors offer that benefit at least, while maintaining a comfortable level of felxibility. Overall, upgrading would be worth the extra money.

Care to share your view on the subject?