I would suggest proceed with WagonR VXL or Cultus VXR (for around 100K) additional. both best fit your requirement have great resale value. A little comparison between these two is below:
New Cultus/Celerio: (VXR)
1- Beautiful and Modern design.
2- Better fuel mileage than WR.
3- Boot is surely spacious than WR.
4- All four windows are power. WR have only front power windows.
Cons:
1- AC performance problem is very frequent, lot of complaints.
2- Dashboard quality is not good, give cheap plastic feeling.
WR (VXL)
1- AC is simply the best, I personally experienced and believe better than Cultus,
2- Better resale value than Cultus at the moment.
3- Best fit in your budget.
4- Commanding view while driving.
5- Dashboard quality is much better than cultus.
Cons:
1-Design is not attractive.
2- Fuel mileage is slightly below cultus.
Choice is yours 