It makes absolutely no difference what bulbs you use, plants will adjust to any light spectrum you give them.
Go for a bulb colour that you like the best.
I like skywhite 880, and 865, as they are very white. if you want a warmer colour try some 830 or 840. You can also use a mixture.
If you want cheap bulbs check this site out.
http
/www.lampspecs.co.uk/Light-Bulbs-Tubes/Fluorescent-Tubes
Also The biggest factor in healthy and fast plant growth is good water flow, co2 and nutrients.
Your t8's are perfectly capable of growing plants and I would not recommend changing to t5's
The reason your plants are not flourishing is probably due to your photoperiod being far to long.
The longer plants are exposed to light the more co2 and nutrients they will need.
If your co2 and nutrients are not matched to your photoperiod then your plants will not grow, in fact the only thing you will grow is algae.
If You changed to t5's the light intensity would be much greater therefor your co2 and nutrient requirement would be much larger.
If you could not provide this then your plants will suffer and you would likely have a massive algae out break.
You also need to ensure water flow is very efficient and reaching all parts of the tank equally. This is to ensure that the co2 you are injecting is reaching all parts of the tank and not just escaping in one corner.
lastly you may want to consider dosing ferts to promote plant growth, again if there are nutrient deficiencies in the water column the plants cant grow.
EI salts are a cheap and easy way to ensure you have the right amount of necessary nutrients in the water at all times.
This is a good starter kit
http/www.aquariumplantfood.co.uk/fertilisers/dry-chemicals/starter-kits/ei-starter-kit.html
To conclude
Get any bulbs you like.
Reduce your photoperiod to around 6 hours a day.
Ensure you have excellent water flow adding power heads/spray bars if needed.
Increase co2 and make sure its at its highest level for when the lights come on.(this is when plants need to most co2) A Good starting point is co2 to come on 2 hours before lights on and turn off 2 hours before lights off. How are you injecting co2 by the way?
Lastly consider dosing ferts to promote growth.
