You better do a little research before you settle on an ISP as it is not easy to switch ISP considering their high 'installation costs' if you are price conscious. Sify has good speed if it works as I use it now but when downtimes occur it can be long time of 3 days to a week before it is resolved. I had a good experience with Airtel broadband for two years (little downtimes if any; fast speed, sometimes even faster than my plan at night) in another locality but after shifting I was forced to use Sify as we have only two ISPs here, Sify and MTNL and comparing the two Sify turns out a bit better.
I have a good experience of ISPs in Delhi as I have tried Tata Indicom, MTNL, Airtel, Sify (currently using) and Hotwire. Airtel wins in my opinion in terms of pricing and speed (Unlimited 256 KBps costs 1050/- taxed added, for home plan here and I got even upto 300 - 450 Kbps occasionally, had 3 days downtime in 2 years because of storm). MTNL has the best speed but the plans are too pricey or limited. Sify is the choice only if you can't get first or can't afford second the downtimes and speed drops are pathetic due to overselling of connections and choking of networks. Tata Indicom and Hotwire lag far behind in service, speed and price.
We really need some laws for better services from broadband, they get around the speed rules by using the word 'upto', like 'Speeds upto XXX Kbps' which practically means 'we can always provide speeds below that and you cannot blame us for that'.