Mbps, not Kbps.

I think you're best off staying. Might check with your neighbors though. If there has been a lot of construction and people moving in or switching to cable that can make the difference. It's pretty much impossible to know what your true speeds are with Comcast. The Powerboost is only temorary and depends on available bandwidth in your area. You benefit from extra bandwidth, but it's only for a few MB's of data. It's a boost, not a continuous fast speed. Speedtest sites just won't give you a true figure for this since they only send a few packets.
DSL adds another router to the mix and it's still all going across the same infrastructure in the end.
Comcast is rolling out faster service as well, the package you and I are on will be seeing faster speeds over the next year or so.
Regardless, what you have is plenty for gaming and hosting. Bandwidth isn't your issue.
Check this, it could help a lot:
Go to your router and check the DNS servers. Compare to the list of servers here, the "domain helper" dns server list:
http://dns.comcast.net/dns-ip-addresses.phpA few months ago, comcast switched customers to dns servers to monitor your habits for advertising purposes. When you put in a bad url, it goes to an advertising based error screen now. You can OPT OUT of this, which should help you out.
You can opt out 2 ways:
1)go to your account webpage and find the opt out. I have not done this, I used method 2.
2)The other (better) way, which is what I did when I first heard about this, is to manually change the DNS servers you use in your router.
Look at that server list I posted and find where your dns server is located. Then go to the link here to the opt out dns server list:
http://dns.comcast.net/dns-ip-addresses2.phpGo to the dns server list in your router and manually change the primary and secondary to the ones on the OPT OUT list. This is legitimate, and the servers are staying at those addresses. You do not want the "domain helper" dns servers.
Alternatively, you could use a 3rd party set of dns servers, which your router may already have listed as an option, but the opt out servers at comcast do a great job.
I'm betting this will help you out.
Another thing:
If you have not enabled QoS (quality of service) for your 360 and pc, then do so. You may be able to put in a MAC address, but you may have to assign a static IP and put that IP address in there. Set the device to High. This tells the router to maintain bandwidth for the device(s) you see as most important. So if your wife has a laptop that she's on while you're gaming, you want your 360/pc to have priority. It's the marriage saver.

Especially important if you host, but also advisable for gaming in general. If you have VOIP, your phone is likely of highest priority and should stay that way, so you don't lose voice quality. It's a good tool to use, but it's only for your LAN, doesn't change anything for issues outside of your gateway.