Need chipset drivers & BIOS experts to help in optimization

I have spent hours on benchmarking my current system and scoured the net for hours on this topic.  But, before i proceed i would like the opinion  of  people  who have  seen  upgrade  efforts  fail.   I bought a new Samsung EVO 850  SSD  (SATA iii)   to upgrade my system.  Current Specs are given below:

1. Samsung  PM 810 SSD ( which is the same as their 470 line) - a Sata II  drive
2. Dell   E6420  with  intel i5  running  Windows  xp  and 4 GB  RAM
3. Nvidia  NVS  4200   display adapter
4. BIOS  version  A06   (current BIOS available is  version  A23 !!)

I have spent hours on benchmarking this system and found that SSD are not optimized.  Probably because my drivers are not upto date and AHCI is not enabled in BIOS.  But, before i attempt all this, i want to give some data here, hoping for feedback.  I used  Passmark,   CrystalDiskMark  and NovaBench  and all were in consensus that both SSDs were not yielding expected results i saw from several others on the internet.  For a sample, here are the results  of  both SSDs :

The  new  Samsung  EVO 850  performance

The  original  PM810 that came with the laptop

Following are my questions:

1. System was never updated in about 5 years, and dell website  only lists  BIOS  versions starting from  A12.   So, i am not sure if  it would be safe for me to  jump  from  BIOS  A06  to  A23  directly, since i do not have all the details  about  versions until  A12.
2. For various reasons, it is not possible to upgrade the current Windows XP Pro  and it is not possible to  reinstall  and start  from  scratch.   The only option i am thinking about is  to  update everything - in the order prescribed by  DELL here.   I would like to know if i am safe,  by updating the chipset drivers,  followed by Intel storage (RST ?) driver  to deal with the  SSD.  I would like to do all this prior to enabling  AHCI  in BIOS.
3. I have made a disk image of the current SSD (onto the new Samsung  EVO 850).  I need step by step instruction  on  how best to optimize  everything  without  crashing  or burning  this system, which is  critical  to me (for  another 6 months, when i will be able to migrate everything  onto a newer platform).

FYI - i am not a newbie, and have built barebone systems from scratch, but that was before 15 years.  The one thing i remember  from those days is that the order of  chipset  driver  installation  could be important. (Separately,  i also need to start another thread to find out  what exactly  are the chipsets  used in  E6420 - if you know a link,  that would save me some time spent on the net to find this info). 

Thanks for all replies.