Basstube will not be a good choice in an Alto. You will have hardly any boot space left. The subwoofer idea looks better to me. Instead of buying online, you should look at aftermarket shops, the prices are almost the same and often, the installation charges are waived off.
For amplifier, you can go for a 4 Channel JBL GTX646 if you want to upgrade in the future (to components, etc.). If further upgrade is not on your list, you can go for a 2 Channel amplifier, from JBL, Pioneer, etc. Do make sure that the amplifier you are getting has enough power to drive your subwoofer.
For subwoofers, you can try the JBL GTX1200, Pioneer Champion Series, RF RS1214. Stay away from Sony, their max power seems very high but they are not at all comparable to the above mentioned brands.
Approximate prices of the products you will need :
- 2 Channel Amp : Rs. 3000+
- 4 Channel Amp : Rs. 4000+
- Basstube (if going for one. Basstubes offer less punch than subwoofer and are good for loud bass and not enjoyable bass, i.e. SPL over SQ) : Rs. 5000+
- Enclosure (for tight bass, you can go for sealed box. Otherwise, a ported one) : Rs. 1000 (approx. price for good quality MDF boxes)
- Wiring (8 Guage wiring kits are readily available. I am using Fusion brand, high end brands have higher price) : Rs. 2000+ (for Fusion, it is 1500, for others it would be upwards of 2500/3000)
- Subwoofer : Rs. 3000 (approx. without bill and warranty. With bill and warranty, expect Rs. 600/800 more)
