Ways To Modify Standard Light Hood?

I'm curious of ways to upgrade my lighting on my 40 gallon. I bought it as a kit and the hood that came with it fits a 24in. t8 bulb. While I don't have too many light demanding plants (Aside from some swords) I really want to improve the lighting to boost my growth as it hasn't been as fast as i was hoping. The bulb that came with the kit is a full spectrum 17watt t8 (Some pretty low intensity...) The hood says 120v and 20 watts on the manufacturer sticker, but even a 20 watt bulb isn't going to be enough. Any ideas? Would fixing in some LED strips work? Can i alter the hood itself to hold a stronger bulb? Any input would be appreciated!

Try these I have one tropical and one reef.they can fit directly into existing light unit if you desire.tropical is 25 w with 6000k.the light is excellent
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Yeah, there are plenty of retrofit LED options now. I used to just take hood like that apart and upgrade the ballasts to allow better tubes, but the LED option is becoming far more sensible now. What you can do depends a fair bit on the shape of the gap you have, naturally, larger gaps tend to lend themselves to a wider array of options, but it does depend a bit.

I really feel like LEDs are just so versatile that it would be the best choice, But unfortunately there is literally no gap... So I can't add on a unit. I was thinking if i did LED's, I would have to incorporate them into the light hood i have now. I just hear that those single strip LEDs are useless. If i squeezed two strips in the fixture would that be enough to boost my lighting? I know all LEDs are different, Im just thinking if i go with this route just get some cheaper white strip LEDs. However, I am really curious about changing the ballast as an option as well. Can I just insert a stronger ballast into the fixture itself and be good? Or is there some extra tech work needed? Sorry for the complete lack of knowledge on lighting guys 

I can't offer assistance with LED other than to say, make sure you get a good unit if you do.  But I have used T8 (basic fluorescent) for 20 years and still prefer it (though a good LED unit would tempt me, if I could be certain).  I don't know your level of knowledge on this, so pardon me if I repeat some of what you already know.
 
First, T8 tubes come in basic standard wattages for each length, so a 24-inch T8 will be 17w (used to be 20w but with the improved manufactured tubes they are more energy efficient with less power).  Watts is simply the measurement unit of the energy needed to light the tube; it is no indication of intensity as this depends upon the phosphors in the tube.  So there is no point in rebuilding the fixture if you stay with T8.  However, there are stronger tubes.  I have a single T8 over my 29g and 33g tanks, and I use the Life-Glo tube which is the most intense light in the tube size that I have been able to find.  I will take a guess that you might have an Aqueon tube that came with the unit?  These are next to useless.  However, a single 24-inch tube over a 40g is really pushing the envelope, but depending upon your plant species this could be sufficient.  I don't know how long you've had the tank and plants, but if the swords are surviving now it might be sufficient to use a better tube.
 
If the tank dimensions limit the tube length to 24 inches, you better option might be to replace the workings with T5.  This light is HO (high output) and equivalent roughly to 1.5 T8 tubes of the same length and spectrum.  I think one T5 would be better than two (one often sees tubes in twin) which would be way too much light.
 
Spectrum is also important.  Plants need blue and red to drive photosynthesis, but studies have shown that adding green to the mix does improve the plant's response (all else being equal), so the "daylight" tubes with a Kelvin between 5000K and 7000K are in this range.  The Life-Glo I mentioned is 6700K.  You can get tubes like this in T8 and T5 (they are not interchangeable in the same fixture).
 
Byron.

Thanks for the info! And yeah by "surviving" that's basically it with my swords. This was the first planted tank i dirted when setting it up about 3 months ago, and i think that's the only thing keeping the swords alive haha they have grown MAYBE an inch since i started this tank. But i'll have to give that Life-Glo tube a look, my only real understanding of lighting was different spectrums are needed of course and the whole "watt to gallon" ratio, So its good to know its not so set in stone