The amp price seems OK but there's no way I'd spend over $250 for a 50X2 unless you absolutely need that 1/2 ohm stable feature.
The sub price is a lot better than standard retail, but you can find them on eBay for under $100.
The Panasonic deck is selling for $299 new on eBay, if your price is from a reputable dealer it's fine.
1999 Buick Park Ave Ultra
Head Unit: JVC KWHDR720
EQ: Audiocontrol EQL
Front Stage: Hybrid Audio Technologies Imagine 5.25
Sub Stage: In process (will be Boston G310)
Amp: Boston Acoustics GTA-704 4 Ch
Rear Fill: Boston SE953 6X9's