From the reviews it appears as far as RO machines are concerned, Aquaguard is a bad bet .
I have been using Hi-tech Water Purifier 10 LPM RO which has International accreditions from American Water Purf. Assn etc(you may check for all these on websites before deciding on makes, If Kent is better for national presence and for people with transferable it should be preferred, otherwise just stick to good regional players with good customer support), for the past 3.5 yrs without any problem, popular in Gujarat and parts of Mumbai/Maharashtra, & they supplied customised RO plants for Pepsi & Cococola as well.
Works with water of even TDS 1500-2500(Designed 1200 TDS) which is quite high for the machine, generating TDS of 120. Upto TDS 150-170 water tastes OK the saltiness starts beyond TDS of 200(WHO norms upto 500). Reputed Mineral waters have TDS of 70-100. Apart from supply water head(Min 6-7 metres), one should also check for hardness of Water. TDS & hardness are different things. RO machines are only for soft water free from hardsalt ions.
I think Kent is also a good brand, but I really I donot have reliable reports of it. Basically all the guys import most of the stuff from US including filters, pumps and membrane. May be Pre-sediment Charcoal block etc can be locally sourced but other things are imported. Any day, use an RO machine fitted with UV filters anywhere, instead of just purifiers(Aquaguard classic etc) cos., it filters many microorganisms excepting some viruses. **Donot compromise on WATER, COOKING MEDIUM/OIL(Prefer 80% rice bran+ 20% Kardi/sunflower brands), SALT(Use Saffola etc though they cost double) and MILK. These are the most common sources of all our basic health issues. Afterall we all earn to spend, spend here first without trying to save., a healthy family & nation is an asset for progress
Check these things rather than brand etc. Use the machine with pre & post flush and weekly cleaning of pre-sediment filter. Two membrane external reverse washes in its lifetime are OK, beyond that change it. I am still using original membrane after 3.5 yrs.
In ROs Any proper service guy can service any machine. No need of OEM provided compatible spares are available now a days