Kenyan Safari - Organise in advance or work it out in Nairobi?

Hi,
I'll be in Nairobi on Jan 18th (Friday) and looking to do a budget-camping safari on the Sunday or Monday for the week. Is it be easy to find a decent company to organise it with at that time of the year when I arrive in Nairobi? The cheapest Ive managed to find online that I can book in advance is a 7 day safari for US$800.
So 2 questions really - is it cheaper to book in the town as opposed to online in advance, and in mid January is it likely to be easy/difficult to find availabilities?
Any knowledge or wisdom on the topic appreciated!
Thanks,
David.

Nairobi will work out much cheaper. There are issues though:

(1) You will waste valuable time running around in search of the best and most suitable deal; and

(2) You may find the ones you like the most are full up.

(3) On the other hand you may be able to grab yourself a bargain - where a company has spare/unutilised capacity, and the "sell by" date is fast looming.

Whether you book online or whilst on the ground, beware of many one-man-and-his-dog companies, who make false promises, and cannot deliver. It is at times worthwhile to pay a little bit more to the big operators, and avoid some of these risks.

You do have another option though. That is to DIY (Do It Yourself). Get to Nairobi, hire an appropriate vehicle, and do the safaris on your own. However, I do not recommend this unless you have driven in the third world before.

Kind Regards,

Mwenyeji