Yes, these both are under my budget but:
1. Both are 110 V and need adaptor to convert 220V to 110V (another accessory and adding more cost)
it looks like their subs below VTF1 do not have dual voltage.
VTF1 onwards supports both regions
2. If I am thinking to upgrade the Sub then I want to go above 150W-200W because of future plans. I may need to upgrade the wattage of Sub couple of years (due to shifting).
So want to upgrade at least 300W or more.
Wattage does not tell the whole story!!
With a sub, one would like one that can
1. Go the deapth - play low
2. Be powerful - play loud
3. Have tight bass - play with good transient response
4. Have flat frequency response - play linearly (reproduces all tones at pretty much the same loudness level)
5. Reproduce the note that is expected to be reproduced - play with high accuracy (you dont want the sub to play 40Hz tone when it is required to play a 50Hz tone)
So with so many factors and cost of sub a constraint, one needs to necessarily sacrifice some features. So you need to choose what.
What a subwoofer does is move air.
1. Lower the frequency, More the air that needs to be moved/pushed to reproduce at the same loudness level that a higher frequency requires. Hence lower frequency reproduction requires larger and larger drivers (subwoofers)compared to higher frequency (tweeters).
2. Hence a smaller 12" driver can push as much air as a 15" driver. But it requires to do a lot more work to achieve what the 15" driver does quite easily with more efficiency.
3. Hence a more powerful amp is required by a 12" driver to do the same work that a 15" driver can. Extending this, one can see that a 15" can be a lot more powerful than the 12" one.
4. A ported sub can play louder than a sealed version. In sealed it is usually only the driver doing the work. In ported the box with the port helps to amplify sound.
5. Larger the ported box, lower the resonant frequency is. Hence lower it can play. Smaller the box, then higher the resonant frequency.
6. Hence you can put a smallish driver with a lowish powered amp in a large ported box and get a pretty powerful sub.
7. On the contrary, you could put the same in a small sealed version and get a pretty quite sub.
8. So to get more power, get a combination of large ported box with either a larger driver or a little more power full amp. And whola! Get all three and you will have a monstrous sub!
9. With limited budget you will not get all three together.
10. And of course you need to consider if its tight, accurate, and linear
A power amp costs money, more power and more money. So you are looking for a large ported since you need power. Moderate size - 10" to 12" sub with low to moderate power amp. And it should serve your needs!
What is ur current sub model? Sealed? Ported? How many watts - RMS / continuous (not dynamic / peak power)?