u can try check out some sub 1k bikes here.
http://bicyclebuysell.com/item/282596/amis-fac-1-2-21speed

more $$$ means maybe more reliable.... depends on many things.... 

used bike u can check bbs lor...

Buying a used bike for RM1,100 when the new one used to cost RM1080 is a bit far fetched isn't it? 

OK, first of all 7 speed means the rear cogs start with 14 tooth and biggest is 28 tooth. 8 speed means it starts with 11 tooth and largest is 30 tooth or sometimes 32 tooth. In terms of high gear, that last 2 gears makes a lot of difference and makes climbing slopes very much easier and in terms of  low gears, on flats and downhills , it will be faster. But sometimes the bike manufacturers will use a smaller crank to make riding even easier and most newbies think, " Wah! so light and easy to pedal" , in actual it is because of the smaller chain ring.

Another point is, the hubs ! 7 speed means using the older fashion freewheel hubs where the freewheel is on the cassette (the rear cluster of gears) where else the 8 gear mean using the freehub that is on the hubs itself. This makes modding to 9 or 10 speed possible. In the case of 7 speed, you need to change the whole hub to move up to 9 or 10 speed. There are 8 speed free wheel cogs but hard to source. 

Hope this helps!

if money concern u and dont want spend much,try the trinx ka2016 either the v-brake or diskbrake.priced below rm1k here in ipoh,the best bang for buck folding bike IMHO.never regret it