i am still debating whether to upgrade my tikit2's gearings and from the advices and by checking sheldon's site here's the possibilities:
1) tikit has 11-28 cassette and with the 53T chainring gear ratio is 30.4-77.4.
2) if i to change it to 11-32 it will give me a gear ratio of 25.1-77.4 (not much difference from the stock 11-28).
3) changing the cassette to 11-34 (megarange) will give me a gear ratio of 26.6-77.4. again not much difference from the stock cassette.
4) if i to change the cassette to a capreo 9-26 this will give me a gear ratio of 32.8-94.6 (an improvement from the original cassette.
5) if i am to change it to an IGH (sturmey archer 8 speed) this will give me a gear ratio of 34.1-103.9. a big jump i may say. i may need a chain tensioner here too. IGH is clean and less maintenance compare to RD.
6) if i go SRAM 3x7 - the range will be from 22.3-105.5 using 7 speed 11-28 cassette.
6) SRAM 3x9 with a capreo 9 speed 9-26 will give you an even higher range from 24-128.9. this will be the ultimate upgrade with a wide range of gear ratio.
so in conclusion - IGH still is the best way to upgrade your tikit (gears/speed). might be too expensive but maybe all worth it. correct me here fellow members if my assumption is wrong.