Could installing DD-WRT speed up my Internet?

I believe that my router's firmware is causing me to get much lower Internet speeds than I should be getting. This is true for general browsing, downloading large files and uploading files. Would installing DD-WRT help me see faster overall Internet speeds?

Diagnosis:

• I know the speed is there, because I'm paying for a high-speed cable Internet connection.
• To confirm that I'm getting what I'm paying for, I temporarily removed the router from the picture by plugging a computer directly into the modem with an ethernet cable; I immediately saw a significant and sustained jump in speed.
• The router hardware itself is capable of handling high speeds. I do get good speeds occasionally, mostly right after rebooting, but they never last for more than a few minutes.

Unless I'm forgetting a link in the chain, firmware is the only thing left that could be causing my problem. This is also the conclusion that my earlier questions (one, two) ended up with. Specifically, I think I'm looking at buggy/inefficient code and/or memory leaks, which DD-WRT might not have.

Most of what I've read indicates that the point of DD-WRT is adding features that out-of-the-box firmware doesn't support (and that I don't need), not improving speed. On the other hand, it seems like every web page and forum post I see about DD-WRT has a slightly different opinion of what it does and how well it does it.

I'm asking about only DD-WRT and not Tomato because Tomato doesn't support my router, a Cisco/Linksys WRT160N v3.

EDIT :
I am using the latest manufacturer firmware. I also noticed something interesting after I posted this question: although I get great speed when I plug into the modem with an ethernet cable, I don't get improved speed when I plug into the router with an ethernet cable. Could that indicate that a firmware change won't help?

As long as your router is on the compatible devices list, it certainly won't make anything worse.

That being said, even if a device does report compatibility, I have noticed on a few routers that they suffer from random wireless issues (mainly dropouts on buffalo devices).

Based on the steps you have already tried, I would first check if there are any manufactured released firmwares. If there are, try that first. If not, go for DD-WRT.

I don't think anyone can tell you for certain if the issue is a bad driver/firmware or a faulty unit as I have seen these symptoms for both and it is impossible to distinguish.