Intel Core i5 6500 - RM 824
Gigabyte H170-HD3 (D4) - RM 486
Corsair 8GB DDR4 2133MHz Value RAM - RM 148
Sapphire R9 390 8GB GDDR5 Nitro - RM 1549
Kingston HyperX Fury 120GB SSD - RM 209
WD Blue 1TB HDD - RM 215
Seasonic M12II EVO 620W - RM 363
Tecware Alpha - RM 219

Total: RM 4013 (ETech price inclusive of GST)

both of them are the same, if you're going to multi task a lot, better take i7, if not, just go with i5
for the graphic, you said that your boyfriend want a good graphic, good graphic : more expensive
8GB ram is enough, based on my experience, dont know bout others 
For the HDD, up to you

You asked for a multimedia PC without stating extra information, so I assume it is for gaming (for your BF), movies, browsing and etc which aren't CPU demanding at all so I went with i5 instead of i7, i7 won't benefit you for those tasks listed unless you are going to do video rendering/editing etc.

You said you must get a good graphics card for gaming, so I included a high end GPU for you, please bear in mind GPU price is always > CPU price, consumer grade i7 costs at most 1.6k but consumer grade GPU can go as high as 4k (and more).

As for RAM, same thing as well, you didn't state what you are going to do with the PC, for basic stuffs (even gaming), 8GB is enough.

1TB HDD is the standard nowadays, 500GB is just around RM 20 cheaper than 1TB which isn't worth at all. Game/FHD movie file size is getting bigger and bigger nowadays, 1TB HDD is just barely enough TBH.

External HDD normally comes with 5,400 RPM only which is slower than internal HDD's 7,200 RPM FYI.

Yes just go ahead