New Swift VDi audio system

Visit several shops and listen to what they offer. 15k would be a tight budget for a decent install. I recommend you go step by step and build a good system. 

1. Head unit: Kenwood/pioneer/JVC etc. with USB and AUX for sure. 1 Din unit would look slim and cost less. 2Din systems usually work the same but cost more. Look for Bluetooth feature ones if you want to sync your phone with it.
2. Front Speakers: Preferably 6" or 6.5" component speakers (Morel maximo's, JBL etc. are affordable ones) at stock location fitted well on a MDF ring. Tweeter placed anywhere around A pillar.
3. Rear Speakers: If you like to have a balanced soundstage (front & Rear) you can go for rear speakers. Preferably 6*9 co-axials placed on a MDF tray at rear. Properly fitted with rubber bushes and tough support from beneath to prevent rattling and sagging respectively.
4. If budget permits, you can go for dampingthe front doors.
5. At later stage you can upgrade the system by adding an amplifier and a subwoofer

Hi Giri,

Thanks a lot for the advice. my plane is to invest only once.
so planing to buy the below.

HU: pioneer AVH-P3400BH

2-DIN Multimedia DVD Receiver with 5.8" Widescreen Touch Panel Display, Built-In Bluetooth®, and HD Radio™ Tuner

Speakers: i'm going to put 8 spk

Front Dash: 2-JBL GT6-S366 (it's going to fit there in Swift-vdi or not)

Door's: 4-JBL GT6-S366

Rear: 2-jbl gto-949

Subwoofer: JBL GT-X1250T

Can you susgest me amplifier

Thanks
Dileep

So many speakers?? But why?? Adding too many speakers will detoriate the sound effect and produce confusing sound stage. If you intend to add so much speakers, it would require multiple amplifiers and sound processor  which will enable the desired effect, but will add a lot to the cost. IMO Opt only for 4 good quality speakers after careful auditioning. I suggest components in front doors and co-axials at the rear parcel  tray or doors. You seem to be going for all JBL speakers, you may also look at different brands. 

HU seems fine. For amps you may look for Rockford fosgate/Kenwood etc.

For the subwoofers audition the jbl/kicker/Rockford fosgate etc

As Giri has rightly said, a combination of four speakers and an optional subwoofer is good enough if it is properly tuned and chosen. So, I would also suggest components at the front and coaxials at the rear.